All eligible ASD participants will be enrolled concurrently in a 16-week, structured, group-based, social skills training program (PEERS®). After screening evaluations, eligible subjects will undergo baseline MRI scanning and behavioral assessments (self- and parent-report measures, videotaped interaction) and then randomized in a blocked schedule to yield 1:1 L-DOPA: placebo assignment, before beginning weekly social skills training. Medication administration will begin simultaneously with social skills training, and subjects will be seen weekly for the 1st 8 weeks, then biweekly for the final 4 weeks for safety assessments, dose titration, and compliance checks. During the 16-week study period, primary behavioral assessments will be repeated at Week 8 and at end of study on Week 16. A second MRI scan will be obtained within + 4 days of last social skills session. A follow-up safety phone call to assess post-study condition will be performed 30 days after completion of double-blind. The rich set of behavioral observations obtained across the 16 weeks will allow the possible identification of early clinical efficacy changes associated with L-DOPA administration, which could add further support for investigating this mechanism in future studies. Results from the project should inform reseacher's understanding of determinants of social dysfunction in ASD and may support further investigation of treatments modulating central nervous system dopamine function as a therapeutic strategy to enhance social functioning in ASD.