Retention of pregnant substance users in treatment is challenging. In a multisite clinical trial, 200 pregnant substance users entering outpatient treatment at one of four programs were randomized to either three individual sessions of Motivational Enhancement Therapy for Pregnant Substance users or three individual sessions normally provided. Retail scrip from $25 to $30 was provided for attendance of research visits but not treatment visits. A post hoc analysis of the non-methadone-maintained participants (n = 175) evaluated the hypotheses that monetary reinforcement for attendance would result in more consecutive, and overall, weeks of attendance of research versus nonincentivized treatment visits. Findings indicate participants were nearly three times as likely to attend 4 consecutive weeks of research visits versus treatment sessions. There was no effect for income while fewer dependents were associated with more consecutive weeks of attendance. Incentives in the $25-to-$30 range may serve to significantly increase attendance and retention.