Clonidine, an α 2 -agonist, was studied in three male human subjects in a multi-dose pilot study in combination with smoking marijuana cigarettes. Marijuana alone caused increases in responses on subjective effect questionnaires and increased heart rate. Pretreatment with single oral doses of clonidine three hours prior to marijuana induced no changes in subjective effects prior to smoking marijuana and did not diminish the subjective effects produced by marijuana. Clonidine did substantially reduce but did not abolish the marijuana-induced rise in heart rate. Based on these preliminary data from three subjects, it is concluded that clonidine does not have therapeutic value in the clinical management of active marijuana abuse.