This report, written for the general public, presents the results of a 15-month study of the health-related effects of marijuana. The introduction describes the goals and procedure for the study, including the composition of the 22-member steering committee and its functions, and the sources of information used for the study, i.e., published scientific literature from 1975 forward, and information and opinions solicited from the public and professional groups. Chapter 1 reviews what is known about the chemistry and pharmacology of marijuana. Chapter 2 deals with the epidemiology and demography of the use of marijuana in the United States. The next three chapters discuss the effects of marijuana on cells, tissues, organs, and biological systems. Chapter 6 deals with behavioral and psychosocial effects. Chapter 7 discusses the present status of marijuana as a therapeutic agent. Chapter 8 describes and analyzes the federal research program on marijuana. A summary includes the principal findings and conclusions of the study, together with suggestions for future research. A glossary of terms for marijuana-related products and appendices with additional study information are included. (Author/MCF)