Highlights are presented on the issue of drug use among servicemen in Vietnam and its aftereffects. Two stages of Vietnam drug use are identified-a period of increasing marijuana use followed by the 1970 influx of highly potent heroin to which 1/5 of the enlisted troops were addicted at some time during their tour. The major contributing factors appear to be: (1) the need of troops in stressful combat situations for self-medication, escape, and hedonistic indulgence; (2) the relaxation of taboos against drug use in the United States; and (3) the availability of illicit drugs at low cost, which was apparently the result of profiteering by a number of South Vietnamese officials. Related to the above was the growing disenchantment with the war and the progressive deterioration in unit morale. These drugs are seen as serving many of the functions performed by alcohol in earlier millitary conflicts. There is no hard evidence that duty performance in Vietnam was seriously affected by drug use. Since 95% of those who were addicted to narcotics in Vietnam have not become readdicted, the situation does not appear to be as severe as originally supposed. Myths as to the persistence and intractibility of physiological narcotic addiction were dispelled. A major negative effect has been the difficulty that soldiers with less-than-honorable discharges due to drug abuse have had in obtaining jobs. Other long-term effects from drug use are less clear and are difficult to separate from the overall effects of the war.