The researchers developed a typology of drug addicts, based on the type, frequency, and seriousness of their criminal activity. The sample consisted of 250 male narcotic addicts admitted consecutively as outpatients at methadone treatment centers in Baltimore and New York between May 1983 and April 1984. Data were obtained from an interview, the Minnesota Multiphasic Personality Inventory (MMPI), and the Raven Progressive Matrices. The 10 data files include 186 variables covering ethnicity, addiction careers, criminal act history, family background, personality profile, and intelligence level. Checks for out-of-range values, missing data, and internal consistency suggest that the data are relatively free of problems. Although 20 variables lack more than 5 percent of their values, most of these are due to the researchers' decision not to include data collected with a Spanish-language version of the MMPI.