This paper presents results from a pilot study of the synergies between the opportunity costs incurred by research participants, participant compensation, and program attendance in a family-based substance use and HIV preventive intervention for Hispanic adolescents in Miami-Dade County, Florida. To estimate parent/caretaker cost per session and cost for the duration of the intervention, we administered the Caretaker Drug Abuse Treatment Cost Analysis Program to a random sample of 34 families who participated in a recent clinical trial of Familias Unidas. The total opportunity cost per parent/caretaker was under $40 per group session, under $30 per family session, and just over $570 for the duration of the intervention. Participants were compensated between $40 and $50 per session and attended more than 79% of family and group sessions. Parents and caretakers incurred a cost of approximately $30-40 per intervention session for which they were adequately compensated. Attendance was very good overall for this group (>79%) and significantly higher than attendance in a comparable uncompensated study group from another recent Familias Unidas trial that targeted similar youth. Findings suggest that incentives should be considered important for future implementations of Familias Unidas and similar family-based interventions that target minority and low-SES populations.