16p11.2 duplication or deletion are among the most common, high-impact risk factors for autism spectrum disorders (ASDs). However, phenotypic variability among individuals with the same 16p11.2 genetic risk factor is wide — including all outcomes from profoundly autistic to essentially unaffected individuals. The purpose of this project is to examine the distribution of additional genetic risk factors for ASDs in the presence of CNVs at 16p11.2, using two parallel tracks of inquiry. The first, genomewide analysis, will be approached genetically through common and rare variant burden analyses, and phenotypically by examining familiality and gender patterning. Second, a focused regional analysis will examine whether variation in the intact chromosome is relevant in deletion carriers. Collectively, these analyses will improve understanding of the mechanisms through which 16p11.2 CNVs create risk for ASDs and, more broadly, the manner in which different types of genetic risk for ASD may behave in concert across the genome.