Reefer Madness was a exploitation film created to demonize "marihuana" (an actual misspelling in the film).
The film tells of two drug pushers, Mae Coleman and Jack Perry, as they sell to adults and kids. The teens and adults are shown growing crazy and acting irresponsible as their usage of "marihuana" continues. A hit and run accident, manslaughter, suicide, attempted rape and murder happen throughout the film.
Throughout the 1970's the film became a midnight movie around college campuses for it's low budget, camp value and blatant fictional "facts" about the Marijuana.
Since then there has been a Musical version and there was a Colorized version of the film made by Legend Films.