Findings on the health consequences of marijuana indicate its harmfulness for pregnant women, drivers, young people, persons with lung disease and heart disorder, and preschizophrenic and schizophrenic people. Recommendations are that marijuana research should focus on the psychosocial factors which influence persons to abuse marijuana; that innovative drug prevention programs, beginning as early as the fourth grade, be established in communities; and that parents and community groups warn youth of the potential harm of marijuana abuse. Regarding the therapeutic uses of marijuana and heroin, the committee endorses and supports the National Cancer Institute's proposal to move THC into its distribution system Group C provided the Drug Enforcement Administration and the Food and Drug Administration exercise guidelines for the drug's distribution, conduct onsite inspections, and monitor records. The committee also recommends that the Department of Health and Human Services encourage researchers to investigate the potential medical uses of marijuana and heroin. Appended supplementary material.