This article reports findings from a study that investigated treatment outcomes among crack/cocaine users over a 18-month period. From a cohort of 229 subjects, three groups emerged: (1) those who had reported ongoing, stable abstinence from crack/cocaine; (2) those who had consistently used during the period; and (3) those who reported cycling between abstinence and use during the follow-up period. Analyses of variance (ANOVA) were conducted to compare the three groups in terms of intake characteristics, including demographic profile, previous treatment, motivational factors, and functioning in seven Addiction Severity Index (ASI) domains. Length of time involved in aftercare and Twelve Step participation after treatment were also contrasted among the three groups. Results showed that subjects who achieved sustained abstinence from crack/cocaine also did better in other domains such as employment, family, legal, and psychiatric than others. Stable abstinence was also significantly associated with a longer period of aftercare and frequent attendance at Twelve Step programs. Logistic regression analyses further estimated the significant impact of the posttreatment factors on the achievement of sustained abstinence. The implications of these findings for treatment services research are discussed.