History
The Lampoon's commercial heyday was roughly 1973-75, with its national circulation peaking at 1,000,096 copies sold of a single October 1974 issue. The Lampoon's 1974 monthly average was 830,000. Former Lampoon editor Tony Hendra's book Going Too Far includes a series of precise circulation figures.
While the magazine was considered by many to be at its creative zenith during this time, it should also be noted that the publishing industry's newsstand sales were excellent during this period. The Lampoon's circulation height coincided with sales peaks for various other magazines such as Mad, Playboy, and TV Guide.

Circulation peak
Most fans consider the glory days to have ended in 1975, when the three founders took advantage of a $7.5 million dollar buyout in their contracts. Also, some of the magazine's contributors left to join the NBC comedy show Saturday Night Live (SNL) around the same time, notably O'Donoghue and Anne Beatts. Even so, the magazine still made money and continued to be produced on a monthly schedule throughout the 1970s and early 1980s, although the magazine was on an increasingly shaky financial footing from the mid-1980s on. Beginning in November 1986, the magazine was published only every other month.
In 1989, the magazine was acquired in a hostile takeover by a business partnership headed by actor Tim Matheson, who had initially gained fame by portraying 'Otter' in the 1978 film National Lampoon's Animal House. During Matheson's tenure he instituted a policy banning frontal nudity in the magazine; frequent full-frontal female nudity had previously been a staple of National Lampoon's style of humor. Facing mounting debts, Matheson sold National Lampoon magazine to J2 Communications in 1991 in order to avoid bankruptcy. J2 was previously known for marketing Tim Conway's "Dorf" videos.
Throughout the 1990s, the number of issues per year declined precipitously. After an attempt to return to monthly publication throughout most of 1991 (nine issues were produced that year), only two issues were released in 1992. This was followed by one issue in 1993, five in 1994, and three in 1995. For the last three years of its existence, the magazine was published only annually. J2 Communications was contractually obliged to publish at least one new issue per year in order to retain the rights to the Lampoon name. The magazine's final print publication was November 1998, after which the contract was renegotiated. In a sharp reversal, J2 was then prohibited from publishing issues.
Though the magazine is no longer in print, its comedic influence on a previous generation of writers and performers was seismic. As co-founder Henry Beard described the experience years later, "There was this big door that said, 'Thou shalt not.' We touched it, and it fell off its hinges."

1975 to the end of the magazine
Since the cessation of the National Lampoon magazine's publication, National Lampoon Inc. continues to, in the words of its prospectus, "develop, produce, provide creative services and distribute National Lampoon branded comedic content through a broad range of media platforms." Since 2002, the company has overhauled its corporate infrastructure several times; the "National Lampoon World Headquarters" is currently located in West Hollywood, California.
National Lampoon still releases books and material under the umbrella of National Lampoon Press. But in 2007, National Lampoon decided to halt its licensing policy in favor of becoming a self-financed comedy production company.

National Lampoon Inc. today
The Robert Altman film O.C. and Stiggs was based on two characters which made several appearances in National Lampoon, including an issue-long story from October 1982 called the "Utterly Monstrous, Mind-Roasting Summer of O. C. and Stiggs." The film was completed in 1984, but not released until 1987 in a small number of theaters, without the National Lampoon name.
Following the success of Animal House, MAD Magazine lent its name to a 1981 comedy titled Up the Academy. But unlike the earlier film, which was co-produced by the magazine's publisher Matty Simmons and co-written by the Lampoon's Doug Kenney and Chris Miller, Up The Academy was strictly a licensing maneuver with no creative input from MAD's staff or contributors. The movie's poor quality and lack of box office success led MAD to abandon its interest in any future film ventures. When the film appeared on cable, all references to Mad magazine were removed from the film, including a statue of Alfred E. Neuman as the school's founder.

Disco Beaver from Outer Space (1978) (TV)
National Lampoon's Animal House (1978)
National Lampoon's Class Reunion (1982)
National Lampoon's Vacation (1983)
National Lampoon Goes to the Movies (1983)
National Lampoon's Joy of Sex (1984)
National Lampoon's European Vacation (1985)
National Lampoon's Christmas Vacation (1989)
National Lampoon's Loaded Weapon (1993)
National Lampoon's Last Resort(1994)
National Lampoon's Deadly Sins (1995)
National Lampoon's Senior Trip (1995)
National Lampoon's Vegas Vacation (1997)
Golf Punks (1998)
Men in White (1998) (TV)
Van Wilder (2002)
Repli-Kate (2002)
Blackball (2003)
National Lampoon's Gold Diggers (2003)
Dorm Daze (2003)
National Lampoon's Barely Legal (2003)
Thanksgiving Family Reunion (2003)
Christmas Vacation 2: Cousin Eddie's Island Adventure (2003)
Going the Distance (2004)
Adam & Eve (2005)
Strip Poker (2005)
Teed Off (2005)
Pucked (2006)
National Lampoon's Pledge This! (2006)
Last Guy On Earth (2006)
Van Wilder: The Rise of Taj (2006)
Dorm Daze 2 (2006)
TV: The Movie (2007)
Teed Off Too (2007)
National Lampoon's Bag Boy (2008)
National Lampoon's Ratko: The Dictator's Son (2008)
National Lampoon's Homo Erectus (2008)
301: The Legend of Awesomest Maximus Wallace Leonidas (2008) National Lampoon movies

Other Media
This show was performed at the Village Gate in 1986, aired on cable in the 80's, and is now available on VHS. It was a sketch-based satire of 1980's culture, told against a frame story of Galahad and Dewdrop, two hippies who took LSD in 1969 and woke up in 1986. The sketches lampooned yuppie culture, health food, the Reagan Administration, airplane hijackings, and psychotherapy.

National Lampoon's Strip Poker
A video-sharing and social networking site featuring viral video content of extreme sports bloopers, "drunken debauchery" and the self-explanatory 'show us your butts'.