The effects of a token economy in modifying the illicit polydrug use of 97 methadone maintenance clients was investigated over a period of two and a half years. Subjects' drug-free urinalysis reports were reinforced with points which could be redeemed to obtain methadone. Each subject's daily dose level varied with the point balance. A multiple baseline analysis showed that when methadone acquisition was in part made contingent upon drug-free urinalyses, illicit drug use declined rapidly. After six months, the token economy group's urines were 14% positive for illicit drugs compared to 39% in the traditional treatment group. As time in treatment increased, illicit drug use further declined. These results suggest a more effective and practical strategy for the treatment of polydrug abusing methadone maintenance clients than has previously been available.