Interview information permitted confirmation of addiction status and addict reclassification into incidence cohorts. The final sample included 238 drug addicts (103 whites and 135 blacks). Data confirmed the predominance of blacks in the addict population. Differences were observed between background characteristics of blacks and whites who were attracted into addiction, but little variations occurred in such characteristics when each racial group of addicts was considered separately. For both races, persons who entered addiction later in the 25-year period were more likely than those who became addicted earlier to have had contacts with juvenile authorities and to have acknowledged criminal activity prior to first drug use. Black addicts appeared to be more successful than white addicts in coping with the problems of addiction. The largest proportion of black addicts had virtually uninterrupted careers in the use of drugs, primarily heroin. They were skillful at avoiding incarceration and appeared to function well in a lifestyle that involved obtaining income from illegal sources to purchase heroin. Among white addicts, there was an increase over time in the proportion classified in a pattern involving addiction less than 50 percent of the 10-year career and incarceration for most of the remaining time. This trend suggested that police became more active or that later addicts were more inept than addicts of earlier years. Both the average black addict and the average white addict received most of their income from illegal sources. Changes in characteristics of addicts over the 25- year period, particularly in the distributional composition of addict career types, suggested a dynamic system requiring continued surveillance of the active addict population. 6 references, 9 tables, and 1 figure