Cheech and Chong meet up by chance on the highway somewhere in California. They go in search of some dope and are accidentally deported to Mexico where in their desperation to get home they agree to drive a van back to the States so they can get back in time for a gig they are due to play. Unaware of the properties from which the van is constructed they make their way back having aquired a couple of female hitch-hikers whilst all the time avoiding the cops whom they are not even aware are following them.
This is a video trailer for the movie.
This is the theatrical trailer in a different aspect ratio and without watermarks.