Subjects (n = 108) who volunteered to participate in a study in which they expected to smoke marijuana were asked, as part of a screening procedure, to rate the harmfulness of a number of illicit drugs including marijuana. Subjects were separated into three groups according to their reported history of use of marijuana. The three groups were: (1) naive users (at least 1 but no more than 25 incidences of use in a lifetime), (2) light users (1 to 3 incidences of use per week), and (3) heavy users (at least 5 incidences of use per week). Groups did not differ in terms of their perceived harmfulness of any of the drugs. Cluster analyses of the results for each group and for the total group indicated three distinct clusters: the drugs perceived to be the most harmful were heroin, morphine, and LSD; drugs perceived to be less harmful were cocaine, amphetamines, barbiturates, and nicotine; and the drugs perceived to be the least harmful were caffeine and marijuana, with marijuana being judged the least harmful of all the drugs.