The Season 2 Sunset on the Beach, September 14, 2005, Waikiki.
Sunset on the Beach is a public service program run by the city and county of Honolulu, Hawaii, which has hosted early screenings of the first three season premieres of Lost. An advanced screening of the final season premiere was held January 30, 2010.  The program features entertainment and food starting at 4:00 pm on the beach at the eastern edge of the Waikiki district, and a video program such as a movie, television program, or documentary begins on a large outdoor screen at sunset. The event has been a source of significant spoilers for the Lost season premieres.
On August 28, 2004, ABC screened the premiere episode of the Lost pilot at Sunset on the Beach, 25 days before the official series premiere on September 22. A day later at the same location, NBC screened the premiere of its series Hawaii at Sunset on the Beach. Both events featured the cast. However a pre-edit version of the pilot episode had been screened publicly more than a month earlier at Comic Con 2004 (attended by Matthew Fox, Dominic Monaghan, and Evangeline Lilly; J.J. Abrams was scheduled to attend but did not appear) on Saturday, July 24. As Lost was not yet a hit, news stemming from these events on the internet was subdued and generally geared toward promotion rather than outright spoilers (e.g.: 1).
The Season 1 Sunset on the Beach premiere was attended by most of the cast: Matthew Fox, Dominic Monaghan, Evangeline Lilly, Jorge Garcia, Maggie Grace, Malcolm David Kelley, Daniel Dae Kim, Harold Perrineau, Terry O'Quinn, Yunjin Kim, Ian Somerhalder, Naveen Andrews, and Josh Holloway. Crew and producers including Damon Lindelof also attended.
After Season 1, Lost was now a hit series with an uncommonly dedicated fanbase, and the Sunset on the Beach event for the world premiere of the second season of Lost drew a crowd of thousands. The now much-anticipated episode "Man of Science, Man of Faith" was screened on Wednesday, September 14, 2005, fully one week before the airing of ABC's official season opener on September 21. This audience represented a much larger attendance than the year before, or for other typical Sunset on the Beach events. Although the screening was accompanied by a continuous downpour of rain that began after sunset, the majority of the crowd stayed through the screening of Lost, although many left soon afterwards, choosing not to stay in the rain for the second part of the double feature, a new episode of ABC's Invasion. An official program on colored paper was handed out for this event, listing both screenings.
Many of the familiar main cast made an appearance at this premiere, including Matthew Fox, Harold Perrineau, Josh Holloway, Naveen Andrews, Dominic Monaghan, Daniel Dae Kim, Jorge Garcia and Maggie Grace. The as-yet unseen Adewale Akinnuoye-Agbaje, Cynthia Watros, and Michelle Rodriguez were also present. Producer Jack Bender and Honolulu Mayor Mufi Hanneman also attended. However, some major cast members such as Terry O'Quinn, Yunjin Kim, and Evangeline Lilly did not attend, as they were actively working on a film shoot for Lost that day, according to Bender.
Due to the fan frenzy from the show's popularity, the screening of Lost was preceded by Bender asking the audience not to give away spoilers to the internet. Despite Bender's pleas, the screening was soon followed by the release of spoilers by Ryan Ozawa on various small websites, and a detailed scene-by-scene summary of the episode at AintItCool.com.
The crowd at the Season 3 event September 30, 2006, Waikiki.
Although the Lost production crew was displeased with the spoilers from the previous year, there was a special Sunset on the Beach preview screening of the Season 3 premiere on Saturday September 30, 2006, which was four days before the officially scheduled ABC airdate on October 4. The event was publicly confirmed on September 22.
Red carpet arrivals began at 5:30pm (with Michael Emerson arriving first), although food and musical events began at 4:00. The events for the premiere of Season 3 began after sunset. As with all Sunset on the Beach events, admission was free, and the screen was erected at the east end of Waikiki, at Queen's Surf Beach. Programs were distributed at food booths, and the ABC booth gave out goodie bags in return for filling out a survey. The attending crowd was composed of thousands of people, with estimates up to 15,000.
Episode one of Season 3, "A Tale of Two Cities", saw its world premiere screening. Also enjoying its world premiere before the screening of the episode was the new Lost music video of the song Demons by Brian McFadden. The screening of the Lost episode was next, followed by a screening of The Nine.
In attendance were the main cast members from last season: Yunjin Kim, Daniel Dae Kim, Terry O'Quinn, Jorge Garcia, Dominic Monaghan, Matthew Fox, Evangeline Lilly, Adewale Akinnuoye-Agbaje, Emilie de Ravin, Naveen Andrews, Josh Holloway, as well as the recently promoted Michael Emerson and Henry Ian Cusick. Also in attendance were the new members of the cast, Kiele Sanchez, Elizabeth Mitchell, and Rodrigo Santoro. Also present were producers including Jack Bender, who also directed the episode, as well as Carlton Cuse, Bryan Burk, and Jean Higgins. No-shows were J.J. Abrams and Damon Lindelof; Cuse explained that they were in California working on an upcoming episode to air in three weeks. Bender also accidentally revealed Henry Gale's real first name, "Ben," during his introductory comments.
On December 19, 2007, Ryan Ozawa reported that the Sunset on the Beach premiere was still on, despite a change in the episode's broadcast television airdate to January 26, 2008.  On January 10, 2008, The Honolulu Advertiser reported that the Season 4 event had been canceled, due to events relating to the WGA strike which had temporarily halted the production of Lost. The event's January schedule confirmed this, as did the television broadcast premiere occurring on January 31, 2008 without a Sunset on the Beach premiere taking place.
There was no Sunset on the Beach screening for the Season 5 premiere in 2009. Due to the world financial crisis, there had been speculation that the event might be canceled, rumors that were finally first confirmed by Jon Lachonis in early November 2008. 
Kiersten Havelock (Emma) and Mickey Graue (Zach) at the Season 6 premiere.
ABC screened the first hour of the two-hour Season 6 premiere episode at Sunset on the Beach on January 30, 2010, three days before the national broadcast premiere on February 2, 2010. Executive producers Damon Lindelof and Carlton Cuse addressed the estimated 15,000 fans with a special message.  The screening began at approximately 6:30 pm on Waikiki beach in Oahu, and was followed by a screening of a new episode of the ABC comedy Modern Family. Those who attended were also able to bid on a signed photo of the entire cast among other items in a special auction at the event. (ABC press release)
Attending cast members were Matthew Fox, Evangeline Lilly, Josh Holloway, Jorge Garcia, Terry O'Quinn, Naveen Andrews, Daniel Dae Kim, Yunjin Kim, Emilie de Ravin, Michael Emerson, Elizabeth Mitchell, Henry Ian Cusick, Ken Leung, Jeff Fahey, Nestor Carbonell, Zuleikha Robinson, Harold Perrineau, Kiersten Havelock and Mickey Graue. Attending producers, writers, and editors included Damon Lindelof, Carlton Cuse, Jack Bender, Jean Higgins, Stephen McPherson, Bryan Burk, Stephen Semel, Adam Horowitz, and Edward Kitsis. Many of the cast signed autographs and posed for pictures with fans. Pictures of the event appeared on the official Lost Facebook page the following day. 
Season 3 event montage by Ryan Ozawa
Season 2 video by YouTube user "Ronsbabe"
Season 1: August 28, 2004
- Lost-TV news - Regarding 2004 Premiere
- Honolulu Advertiser - short article on premieres for Lost and Hawaii with the cast on August 28, 2004. As Lost was not yet a hit, no followup article was printed the next day on August 29.
- Sunset on the Beach - Honolulu City event listing for August 28, 2004
- Lost-Media - Photo album from Season 1 Premiere at Sunset on the Beach
Season 2: September 14, 2005
- Honolulu Advertiser - Lost Cast Showered With Love (September 15 2005)
- Sunset on the Beach - Honolulu City event listing for September 14, 2005.
- AICN (Ain't It Cool News) - "A liquid glowing ominously" FEAR NOW THESE SPOILERS!! LOST 2.1!! - Season 2 Premier spoiler. Although dated September 21, 2005, this article is a site repost of a nearly identical spoiler on September 15.
- HawaiiUp Podcast #25 - Spoiler podcast from Ryan Ozawa, formerly producer of The Transmission fan podcast.
- Lost-Media - Photo album from Season 2 Premiere at Sunset on the Beach
- YouTube - Fan video from the S2 premiere
Season 3: September 30, 2006
- Sunset on the Beach - Honolulu City event listing for September 30, 2006. This listing confirms the upcoming Season 3 preview.
- themisfitishere blog - Photograph of a VIP-area access ticket of the Sept. 30 2006 event.
- Honolulu Star-Bulletin - Sep 24, 2006 article on the event.
- Lost-Media - Photo album from Season 3 Premiere at Sunset on the Beach
- Dharmasecrets forums - spoiler thread
- Honolulu Star-Bulletin - October 1, 2006 article by Katherine Nichols on the Sep 30, 2006 event - "Lost premiere draws thousands"
- Honolulu Advertiser - October 1, 2006 article by Michael Tsai on the Sep 30, 2006 event - "Thousands turn out for stars, answers!"
- YouTube - Video montage from Ryan Ozawa of The Transmission podcast.
- Lost Virtual Tour - photos and commentary
- Lost Spoilers Blog - Detailed spoiler episode summary
- Honolulu Star Bulletin - October 2, 2006 article, continued coverage of the event. Some extremely minor spoilers regarding the episode (essentially putting to words the various ABC promotional photos and television trailers for this episode, and nothing more).
- Honolulu Advertiser video - Comments from the event stage from the producers, from Honolulu Advertiser's photographer Rebecca Breyer, hosted on YouTube
- Lostblog.net - (October 3, 2006) - Lostvirtualtour.com's narrative hosted on Lost Blog
- Maleko's Room - Interviews and gallery from DJ Hawaii radio station Star 101.9
- ABC Medianet - official press photos from ABC
- eXtra TV - video interview by Tanika Ray
- Letter from Lost - Full page letter printed October 15, 2006 in the Honolulu Star-Bulletin, printed on the back of the first section of the paper, it's a thank you letter from Lost to Hawaii.
- October 5, 2006 - TV.com video interview of the Sep 30 event (Jorge Garcia, Matthew Fox, Evangeline Lilly) 
- Honolulu Advertiser - October 29, 2006 - "Pair of opposites keeps 'Lost' attractive" - article with photo from premiere