The relationship between the reinforcing quality of the first drug experiences and eventual habits for a variety of drugs was studied in 42 male drug abusers who were predominantly opiate addicts. These subjects volunteered for drug studies carried out by the Addiction Research Center. The degree of reinforcement they derived from their first drug experience was related to their subsequent habit. This was true for alcohol, barbiturates, minor tranquilizers, cocaine, stimulants, marijuana, glue or solvents, hallucinogens, opiates other than heroin and heroin. Positive but non-significant correlations were found for coffee and major tranquilizers. The correlation for cigarettes was contrary to expectations. Of the components to the index of reinforcement, degree of liking of a drug on the first occasion was most related to the subsequent habit. The greatest initial reinforcement scores were found for heroin, cocaine and opiates other than heroin. drugs which were not well liked on the first occasion included major tranquilizers, cigarettes, coffee, and glue.