We conducted an online survey of adult health care providers at Kaiser Permanente Northern California and semi-structured interviews with a subset of physicians. The survey assessed providers' ability to recognize autism spectrum disorder (ASD), asked them to rate their autism knowledge, comfort level in treating affected patients, and evaluated training and resource needs. 922 providers completed the survey (response rate 25.3%), and 9 were interviewed by telephone regarding their autism training and experiences caring for patients with autism. Most providers reported lacking skills and tools to care for this adult patient population. A high proportion of adult providers were not aware that they had patients with ASD. These findings underscore the need to educate physicians caring for adults with ASD.