Epidemiologic data has implicated a strong genetic component in autism spectrum disorders (ASD). This study will examine the most consistently identified chromosomal region in autism, 7q21-32, to try to identify the gene on this chromosome that is linked to ASD. A multi-pronged approach will be used, including a comprehensive scan for single nucleotide polymorphisms (DNA sequence variations) in the region and evaluation of candidate genes by haplotype mapping, mutation analysis, methylation and cytogenetic studies and, where possible, for transcription and gene expression. Particular attention will be paid to genes surrounding the regions on chromosome 7 that were breakpoints in the translocation process. Ultimately, the goal of these studies is to identify the gene on chromosome 7 that is linked to autism, representing a fundamental step in understanding the genetic basis of the disorder.