Recent advances in the genetics of autism spectrum disorders (ASDs) are offering new valuable insights into molecular and cellular mechanisms of pathology. At the same time, the emerging data challenge long-standing diagnostic conventions and the notion of phenotypic specificity. This review addresses the particular issues that attend gene discovery in neuropsychiatric and neurodevelopmental disorders and ASDs in particular, summarizes recent findings in human genetics broadly that are driving the reevaluation of the conventional wisdom regarding the allelic architecture of common psychiatric conditions, reviews selected discoveries in ASDs and their relevance to models of pathology, highlights the conceptual and practical issues raised by the observation of a convergence of ASD genetic risks with distinct psychiatric disorders, and considers the important interplay of studies of neurobiology and genetics in clarifying and extending our understanding of social disability syndromes.