This review synthesizes drug abuse outcome studies that included a family-couples therapy treatment condition. The meta-analytic evidence, across 1,571 cases involving an estimated 3,500 patients and family members, favors family therapy over (a) individual counseling or therapy, (b) peer group therapy, and (c) family psychoeducation. Family therapy is as effective for adults as for adolescents and appears to be a cost-effective adjunct to methadone maintenance. Because family therapy frequently had higher treatment retention rates than did nonfamily therapy modalities, it was modestly penalized in studies that excluded treatment dropouts from their analyses, as family therapy apparently had retained a higher proportion of poorer prognosis cases. Re-analysis, with dropouts regarded as failures, generally offset this artifact. Two statistical effect size measures to contend with attrition (dropout d and total attrition d) are offered for future researchers and policy makers.