The cognitive science of religion is a new field which explains religious belief as emerging from normal cognitive processes such as inferring others’ mental states, agency detection and imposing patterns on noise. This paper investigates the proposal that individual differences in belief will reflect cognitive processing styles, with high functioning autism being an extreme style that will predispose towards nonbelief (atheism and agnosticism). This view was supported by content analysis of discussion forums about religion on an autism website (covering 192 unique posters), and by a survey that included 61 persons with HFA. Persons with autistic spectrum disorder were much more likely than those in our neurotypical comparison group to identify as atheist or agnostic, and, if religious, were more likely to construct their own religious belief system. Nonbelief was also higher in those who were attracted to systemizing activities, as measured by the Systemizing Quotient.