Current primary care models are inadequate for adults on the autism spectrum. The Center for Autism Services and Transition (CAST) clinic was developed in 2014 using feedback from parents of adults on the autism spectrum and patient-centered medical home principles. We evaluated the reach of CAST's services. As of January 2021, 858 patients were seen in CAST. Many continue to receive primary care from the CAST clinic. The program has undergone staffing changes but continues to accept new patients. We have added services such as "happy visits," pre-procedure videos, and telehealth visits. CAST provides one example of how to improve primary care for adults on the autism spectrum. More research is needed to assess the effectiveness of the CAST model.