In California, jobless hippie and stoner Anthony "Man" Stoner (Chong) is kicked out of his house by his rich and classy father. He drives off in his father's car, which breaks down, and Anthony is left stranded near a beach, left to sleep in a ditch over night with his belongings.The next morning, Chicano stoner Pedo De Pacas (Cheech) sets off from his Mexican-family-house in his low-rider car looking for love with errands to run. Pedro drives along the beach where he tries to pick up ladies and sees Anthony with melons stuffed under his shirt. Assuming that Anthony is a large-breasted woman, Pedro drives his car around and tries to pick "her" up, only to be horrified when he discovers Anthony is just a guy looking for a ride.Feeling bad (and liking that Anthony likes his car), Pedro gives Anthony a ride, just missing being caught by the police. While driving, the 2 take a liking to each other being that they both like smoking marijuana. Pedro offers Anthony a small joint, while Anthony shows Pedro a huge joint, made out of dog feces (being that the dog ate Anthony's stash). The 2 smoke the joint and get incredibly high, followed by Pedro accidentally swallowing a lot of acid. The car crashes into a light pole, and the 2 are arrested and the car towed away. In a small courtroom trial, the 2 are being prosecuted when Anthony, still high, begs for water. Pedro grabs some of the judge's "water" for Anthony, only to have Anthony spit it out, revealing it to actually be vodka. With the judge taken away, Pedro and Anthony are let off free.The next morning, after Anthony meets (and argues) with Pedro's band (being that Pedro is a guitarist/singer and Anthony is a drummer), the 2 set off to score some weed. However, the town is dry being that many people are smoking pot these days. The 2 visit Pedro's cousin Strawberry, who is a retired war veteran who is a little messed up in the head and has a large "birth mark" on his face. Anthony stays in Strawberry's messy apartment while Pedro and Strawberry go off on a motorcycle to get weed. While in the apartment, Anthony meets Strawberry's roommate, a coke-head who throws a large drug party in the apartment. Meanwhile, Strawberry has a war flash and loses his mind and jumps off the motorcycle, sending Pedro crashing. When he crashes, he sees cops hiding outside the apartment, ready to bust in and arrest the druggies at the party. Pedro tries to warn Anthony via phone, which is bugged, and the party is busted. Pedro infiltrates the bust dressed like a repossession man, claiming he's there to repossess the stuff. The cops buy the story, and Pedro rescues Anthony.After that, the 2 visit Pedro's friends' place where the 2 get stoned, but not so much being that the weed is bad. At that point, immigration busts in, being that Pedro's friends calling immigration on themselves to get a free ride to a wedding in Mexico. Of course, Pedro and Anthony, despite their efforts to hide, get caught and deported to Tijuana as well.While in Tijuana, Pedro calls his uncle and gets the address of a upholstery shop and arranges to pick up a van to drive back to America. But after getting fast food over the address, the 2 arrive at the wrong place- an upholstery shop which is actually a marijuana plant in disguise. The factory actually makes materials out of solid and liquid marijuana, which is then smuggled across the border. The marijuana-made things made there are worth up to $9 million, and is heavily watched by police, led by Sargeant Stedanko. Pedro and Anthony show up to the factory, unaware of what it really is, and say they're there to pick up "the van". Rather than getting an actual van, the stoners get a huge green van, made from marijuana, top to bottom. From the steering wheel, the tires, the doors, the gas tank, to the very structure of the van itself, its all made of pure solid and liquid marijuana- and the guys have no idea they're smuggling it into America.The stoners drive their marijuana van to the border where they're stopped by police. Anthony is smoking a joint, which he throws out the window into the window of a car full of nuns. Pedro and Anthony are almost caught, when the police discover the joint in the nuns' car. The car is taken away and the nuns searched and arrested by Sgt. Stadenko and his police officers. Unaware of what they did, the hippies drive through the border back into America in their van, stopping at the border patrol station so Anthony can use the restroom. In the restroom, Anthony pees next to Stadenko and accidentally "shakes himself dry" on the sergeant's leg before leaving. An angry chief leaves the bathroom to have the officers tell him that they were wrong about the nuns, its actually 2 hippies in a big green van. Realizing who Anthony must have been and the green van was completely ignored, Sgt. Stadenko and 3 officers get in the police car and set off on the roads after Pedro and Anthony.It isn't long before the cops get sight of the marijuana van being driven by a Chicano and a hippie. They speed up, only for Pedro to get view of 2 hitch-hiking young ladies. He swerves the van across the highway, causing for the police to accidentally shoot the tires off their own police car. Pedro and Anthony (who have no idea cops are pursuing them), pick up the hitchhikers and drive off. Pedro and one of the hitchhikers make out in the back while Anthony drives with the other hitchhiker. Meanwhile, Stadenko has fixed the tires and has continued the search, having no idea where the stoners could've gone.Pedro and Anthony learn from the hitchhikers that they are actually heading for a battle of the bands concert in Los Angeles, with the winners getting a record contract. Excited, Pedro and Anthony decide to go to the battle of the bands with the ladies and compete. But first, they need to stock up on some weed. The 4 stop the green van at a police station, where a stoner female cop goes to get the 2 ladies' illegal marijuana. Pedro and Anthony use this time to play with the intercom and police transmitter, taunting Sgt. Stadenko over the radio. At this point, Stadenko is really upset, and he and his cops show up at the station. Stadenko goes to use the bathroom, where Pedro is. Pedro too "shakes himself dry" upon Stadenko's leg as Anthony did earlier and leaves, making Stadenko angrier.Pedro and Anthony and the girls, acquired with weed, return to the marijuana-made van and head on to the road again to Los Angeles. However, unknown to the 4, the gas coming out of the van is pure marijuana smoke, getting anyone who inhales really high. This occurs at the police station where someone near the van gets high and a case of the munchies, ordering multiple hamburgers from a nearby fast-food stand. While they drive along the highway, the smoke from the van spreads out the exhaust pipe, getting all driving by with their windows down really high. At one point, a police officer on a motorcycle speed after them, but inhales the smoke and gets high, and forgets what he's doing. Pedro, Anthony, and the women get away, but the high cop is found by Stadenko, and, while high, reveals where the marijuana van headed off to, and Stadenko follows after the van.The van soon arrives in Los Angeles to the Roxy Theater where the battle of the bands takes place. Pedro and Anthony head into the theater and enter the competition, leaving the ladies behind. While inside getting ready, Anthony isn't feeling good so he takes some pills given to him by the hitchhikers- which turns out to be acid. Anthony slowly gets high, and the smoke from the van enters the vents backstage and gets both Pedro and Anthony very high as they prepare to go on. As a result, Pedro dresses in a pink tutu and a Minnie Mouse bow, while Anthony dresses in a red Quaalude.Meanwhile, outside, Stadenko and crew have found the theater, and try to get inside, but are shooed off by real policemen, being that they've left their badges in the car and don't have tickets. The van is almost towed away and Stadenko tries to take the van but is denied the right to have it taken away. A billion-dollar bust, gone. Stadenko and the cops hang around the van waiting for Pedro and Anthony, but get high off the smoke, and Stadenko is soon turned into a huge stoner (as seen in the movie Cheech and Chong's Nice Dreams) as the van burns down into nothing but marijuana smoke, getting everyone in Los Angeles really high.Back in the theater, it is Pedro and Anthony's turn to go on. The van has nearly burned down and all the smoke entering the vents has gotten everyone in the theater high. The 2 go on stage, really high from the van smoke, and almost knock over the band equipment. The 2 then play their rock song "Earache My Eye" (an actual song on a Cheech and Chong record), about a gay boy trying to live his life. The song is a big smash (even though Pedro had just written it and sang it as he went on), and Pedro and Anthony win the contest and the record deal, although still very high.Days later, Pedro and Anthony are back in California from their whole drugged-up adventure, driving in Pedro's low-rider on the street next to the beach where they first met. They're happy, talking about their new record deal and all the possibilities that can happen, when they decide to smoke some hash. Anthony smokes some and hands it to Pedro, who accidentally drops it in his crotch. Pedro's crotch starts burning up and he freaks out as he and Anthony try to put it out. The car crashes as the hash starts burning up, and Pedro and Anthony (Cheech and Chong), their car, and the record contract are all left, well, up in smoke.