The article examines reasons for divergent recovery rates (ranging between 7 and 90 percent that are documented in studies of alcoholism-treatment outcome. It stresses the importance of the role of client characteristics, program length, setting and intensity, treatment methods, client-treatment matching, and relapse prevention strategies. Most important is comparison of treatment outcomes in consideration of characteristics of patients, particularly offenders with high severity of psychiatric symptomology and a diagnosis of alcohol or drug abuse or dependence. Studies with a strong theoretical basis for the choice of patient and treatment variables have produced the most dramatic effects of patient and treatment matching and account for 16 percent to 30 percent of the treatment outcome variance. These results suggest that treatment outcome results for substance abusers will improve with increased knowledge about optimal matching of clients to treatment modality and prevention strategies. 12 references (Author abstract modified)