Autism is a strongly genetic disorder, with an estimated heritability of greater than 90%. Nonetheless, its specific genetic etiology remains largely unknown. Over the past several years, the convergence of rapidly advancing genomic technologies, the completion of the human genome project, and successful collaborative efforts to increase the number of deoxyribonucleic acid samples available for study have led to the first solid clues regarding the genetic origins of autism spectrum disorders. This article addresses the obstacles that have confronted gene discovery efforts and reviews recent linkage, cytogenetic, and candidate gene association studies relevant to autism spectrum disorders. In addition, promising avenues for future research and the potential contribution of emerging genomic technologies are considered.