Heroin use by American soldiers in Vietnam differs significantly from heroin use in the United States. Users in Vietnam are of many personality types and backgrounds and most have slight previous drug experience. Heroin in Vietnam is strong and easy to get. It is smoked, snorted, or ingested; until recently mainlining was rare. Some users function well, others poorly. Most important, users are members of small heroin-taking groups who are disillusioned with the "non-war" and the Army in contrast to the "loner" user in the United States. In June 1971 the Army began a mandatory urine-testing program to detect heroin. Rehabilitation and treatment efforts, largely ineffective, included a hard-sell education campaign, centers organized by ex-addicts, programs emphasizing physical detoxification, psychiatrically oriented groups, and penal institutions. Reports indicate that group setting is an important factor in every aspect of the user's response including the withdrawal reactions.