No single treatment approach is effective for all persons with alcohol problems. A more promising strategy involves assigning patients to alternative treatments based on specific needs and characteristics of patients. Project MATCH is a multisite clinical trial designed to test a series of a priori hypotheses on how patient-treatment interactions relate to outcome. Two independent but parallel matching studies are being conducted, one with clients recruited from outpatient settings, the other with patients receiving aftercare treatment following inpatient care. Patients are randomly assigned to Twelve-Step Facilitation, Cognitive-Behavioral Coping Skills, or Motivational Enhancement Therapy. Subjects are followed at 3-month intervals for 1 year following completion of the 12-week treatment period and evaluated for changes in drinking patterns, functional status/quality of life, and treatment services utilization. Interaction effects with selected patient characteristics will be studied. Project MATCH will provide a rigorous test of the utility of patient-treatment matching in general and, depending on the specific a priori hypotheses validated, will have important implications for clinical practice.