This research monograph, written for community officials and planners of drug abuse prevention programs, presents straight line projections on the possible extent and kinds of nonmedical drug use for young adults (18-25 years old) that can be expected in the future. Projections are made based on current young adult drug abuse and population trends. The purpose of the study and methodologies are described in the introductory chapter. Chapter 2 comments on demographic trends in family status, education, income, geographic distribution, race, ethnic composition, total population size, and age composition. In chapter 3, sources of data on drug abuse are reviewed and evaluated for their usefulness in making future projections. The remainder of the monograph presents the projections, in text and tables, for marijuana, inhalants, hallucinogens, cocaine, heroin, and other opiates. Data are given for total numbers and for percentages of 18 to 25 year olds who may be expected to use these drugs in 1985, 1990, and 1995. Trends are further tabulated by sex, race, and residence in metropolitan or nonmetropolitan areas. Numerous tables and an annotated bibliography on demographic trends and forecasting techniques supplement the text. (BL)