Given the increasing prevalence of autism and the importance of early intervention, it is imperative that primary care physicians (PCPs) have a thorough knowledge of autism in order to offer families appropriate guidance and support. This study comprised a systematic review of research assessing PCPs' knowledge of autism and evidence-based interventions for individuals with autism. Results indicated that PCPs in a majority of studies had inadequate knowledge of autism and its associated treatments. A variety of variables were associated with PCPs' knowledge including personal experiences with autism, continuing medical education on autism, and years of clinical experience. Results are discussed with regard to their implications for further education in autism for PCPs and future research.