This study evaluated the efficacy of a contingency management (CM) intervention to promote smoking cessation in methadone-maintained patients. Twenty participants, randomized into contingent (n=10) or noncontingent (n=10) experimental conditions, completed the 14-day study. Abstinence was determined using breath carbon monoxide and urine cotinine levels. Contingent participants received voucher-based incentives for biochemical evidence of smoking abstinence. Noncontingent participants earned vouchers independent of smoking status. Contingent participants achieved significantly more smoking abstinence and longer durations of continuous smoking abstinence than did noncontingent participants. These results support the potential efficacy of using voucher-based CM to promote smoking cessation among methadone-maintained patients.