The author studied patterns of drug abuse in Viet Nam among three groups of enlisted men—those finishing a 12-month tour, those who had been psychiatric outpatients, and new arrivals. Among those in the first two groups using hard drugs and/or marijuana, a majority used hard drugs. Of the men using drugs in the first two groups, 34 percent began doing so in Viet Nani, while 58 percent of the men using drugs in all three groups began as civilians before entering the military. The implications of these findings are discussed in terms of the military and of society.Abstract Teaser