['The aim of this study was to determine how the treatment needs and outcomes of polysubstance-using patients entering opioid-substitution treatment (OST) may be affected if the patient had a parent with substance-use problems.', 'This prospective observational study examined outcomes of 255 patients (97% male) entering OST at eight clinics in the Veterans Health Administration. Self-reported substance-use outcomes in the first year of treatment were compared between patients with (n = 121) and without (n = 134) a parent with substance-use problems. The association between receipt of practice guideline-recommended elements of care and treatment outcome was examined.', 'Parent history-positive patients had greater drug use at 6 months, but by 12 months they had reduced their drug use to the same extent as parent history-negative patients. Ongoing methadone (Dolophine, Methadose) maintenance was associated with improved outcomes of drug use in parent history-negative patients; however, parent history-positive patients who ended methadone maintenance reduced drug use as much as those who continued treatment. The association between treatment received and outcome differed in these populations. In parent history-negative patients, reduced severity of substance use at 1 year was predicted solely by receiving methadone for a greater number of days. In parent history-positive patients, reduced severity of substance use was predicted by receiving methadone for fewer days, by greater satisfaction with and receipt of counseling services, and by lesser tendency for providers to encourage a reduction in methadone use.'] Do different components of opioid-substitution treatment predict outcomes of patients with and without a parent with substance-use problems?