Although autism spectrum disorders (ASD) are clearly heterogeneous, many risk factor studies often consider ASD as a single entity. However, there is increasing evidence that different genetic and environmental risk factors may predispose to different subtypes of ASD. The purpose of this session is to examine the epidemiological, familial, and genetic evidence regarding how patterns of ASD risk may vary by conditions often noted to co-occur with ASD, especially intellectual disability (ID). The first talk will provide an overview of environmental risk factors that have been observed to have divergent associations for ASD with versus without ID. The second talk will discuss how paternal intelligence and child ASD are associated in a Swedish sample, taking into account co-occurring ADHD and ID. The third talk will discuss how ASD risk is related to cross-disorder risk of other psychiatric diagnostic groups, using a sibling design study from Israel. The fourth talk uses genetic data from two well-characterized samples to examine how common polygenic risk for ASD, educational attainment, schizophrenia, and intelligence are related. Attendees will come away with a greater understanding of the nosologic and etiologic implications in considering ASD with and without co-occurring ID.