Bolstered by evidence of acceptability, feasibility, and promise from a pilot study, the Social ABCs was subsequently evaluated in a two-site RCT, demonstrating the efficacy of this caregiver-mediated intervention for toddlers with suspected or confirmed ASD. This study found increases in child vocal responsiveness, vocal initiations, parent smiling, and a trend toward increased social orienting in toddlers with suspected or confirmed ASD. Findings also demonstrated that caregivers attained fidelity relatively quickly, rated the intervention as highly acceptable, reported increased feelings of self-efficacy, and did not report increased stress associated with the burden of learning and providing the intervention.