 - After 3 weeks of methadone treatment, participants will have 15 weeks of EMA in which they will record both event-triggered cravings and daily responses 3 per day. EMA will consist of event-triggered recordings initiated by participants whenever they use heroin or cocaine, or whenever they feel an urge to do so and random-signal-triggered recordings 3 per day. During EMA, participants will begin a voucher-based program to encourage abstinence from heroin and cocaine. 