Members of the Lambda Lambda Lambda fraternity at Adams College go to the United Fraternity Conference in Fort Lauderdale, Florida. However, upon arrival at the Royal Flamingo Hotel, the five Tri-Lambs – leader Lewis Skolnick, nearsighted Arnold Poindexter, shy Harold Wormser, flamboyant Lamar Latrelle, and vulgar Dudley “Booger” Dawson – learn their reservations have been canceled. Front desk clerk Sunny Carstairs checks with the acting hotel manager, Buzz Mussinger, who reports that he does not want “nerds” staying at his hotel. The five find a room at the rundown Hotel Coral Essex on the other side of town, but the Alpha Beta fraternity plots to keep them from attending the conference. Alpha Beta leader Roger Latimer, who is also head of the United Fraternity Conference, sends the five Tri-Lambs an invitation to a pre-conference barbecue in the Everglades. When the nerds arrive, they stumble into what appears to be a Seminole Indian ritual ceremony. In reality, the Native Americans are Alpha Betas in disguise. They force the Tri-Lambs to strip to their underwear, then send them away. After walking five miles back to the hotel in their underwear, some of the Tri-Lambs want to return home, but Lewis Skolnick insists they stay. The next day, as the conference opens, the Tri-Lambs are forced to sit on the floor when there is no table available for them. During a parliamentary proceeding, Roger Latimer proposes a vote on Proposition Fifteen, which would set physical standards, including muscles, strength, height, and appearance, for membership. Lewis objects, but the other conference attendees are too busy partying. Realizing they need to fight this proposition, the Tri-Lambs rig the Hotel Coral Essex neon sign to read “Hot Oral Sex” and attract a large crowd to a party where they perform a “No on Fifteen” musical rap, urging conference attendees to vote against the bill. The next day, the conference removes the Prop Fifteen vote from the agenda. To apologize for their behavior, the Alpha Betas give the Tri-Lambs their suite at the Royal Flamingo Hotel. Meanwhile Roger Latimer plots with hotel manager Buzz Mussinger to get rid of the Tri-Lambs permanently. They arrange for Sunny Carstairs and some of the other female employees to take the Tri-Lambs out on the town, and Roger gives the women the keys to his car. After a few hours on the beach, the Tri-Lambs leave to buy more beer, using Roger’s car. However, Roger reports his car stolen, and police arrest the Tri-Lambs for grand theft auto. Meanwhile, at the Royal Flamingo, employee Stewart Lipsey looks for the Tri-Lambs. The Alpha Betas tell him they are in jail and toss him over the balcony into the pool. When Stewart tells Sunny what happened, she bails them out of jail. As the five fraternity brothers leave, however, the Alpha Betas kidnap them, along with Sunny and Stewart, and toss them into the back of a van. The group is taken on a boat and thrown overboard near a deserted island in the Florida Keys. When Fred “Ogre” Palowatski, a burly but not terribly bright Alpha Beta, announces he cannot wait to brag to the other conference attendees about what they have done to the Tri-Lambs, Roger Latimer tosses him overboard as well. Ogre is unable to swim, so Tri-Lamb Harold Wormser rescues him, and they become friends. As the castaways collect firewood, Booger finds marijuana plants, and the group gets “stoned” around the fire that night. Later, Lewis has a dream in which he is visited by his fraternity brother Gilbert Lowe, who missed the conference due to a broken leg. Gilbert warns Lewis that the conference will vote to kick the Tri-Lambs out of the conference on moral grounds stemming from the grand theft auto charges. The next morning, they discover a secret bunker with military supplies left by a Cuban military officer following the Bay of Pigs invasion. Manning an amphibious vehicle, they return to the hotel just as attendees are voting to expel the Tri-Lambs from the conference and terminate their charter. When Sunny reports that Roger Latimer orchestrated the Tri-Lambs' arrest, Lewis Skolnick punches Roger in the face, sending him into the pool. Lewis and Sunny kiss. Meanwhile, Ogre quits the Alpha Betas and joins Lambda Lambda Lambda. The guys give Ogre a pair of glasses and a pocket protector to signify he is now one of them.