We conducted a survey of beliefs about autism among the general public in the United States and Canada (n = 823) and among individuals working in childcare facilities in the state of Idaho (n = 176). Results included the following. Almost all respondents correctly believed that autism’s primary causes are genetic and neurological (not parenting, drugs, or current diet), that it can be identified in early childhood, and that helpful interventions exist. Respondents generally distinguished diagnostic from non-diagnostic traits, but approximately half incorrectly labeled constant squirming as diagnostic and difficulties in making friends as non-diagnostic. College graduates and childcare workers were more likely to have learned about autism in professional/academic settings and to correctly recognize diagnostic traits. Of concern, 10% of respondents considered vaccinations to be among the two main causes of autism. Accurate public understanding of autism spectrum disorders can facilitate early identification and effective intervention; our results suggest that efficient channels for conveying accurate information include broadcast and online media (from which the general public, especially members of ethnic minority groups, were most likely to learn about autism), and professional development courses for childcare providers.