Testimony was received from Dr. Gabriel Nahas of Columbia University, Dr. Norman Zinberg of Harvard University, Dr. Sidney Cohen of the University of California at Los Angeles, and William Pollin, Director of the National Institute on Drug Abuse. Although the witnesses disagree as to the precise effects of marijuana on the human body as evidenced in contemporary research, there is some consensus on the general effects of the drug. There is agreement that the effects of marijuana on the reproductive system are such that pregnant women should not use the drug. The effects on coordination are such that driving under the influence of marijuana can be hazardous. Young people should be discouraged from using the drug, and individuals with lung disease should not use marijuana because of its irritating effect. People with heart disorders may be further impaired because of the increase in heart rate associated with marijuana use. Preschizophrenic and schizophrenic people may develop or exacerbate a psychotic break in connection with marijuana use. Infrequent use (less than once a week) by adults will probably not result in ill effects unless the smoker experiences one of the uncommon, acute reactions. The therapeutic potential of marijuana, particularly for the management of nausea and for wide-angle glaucoma should be studied further. Prepared written statements by the witnesses are included.