Secretin is a peptide hormone involved in digestion that has been studied as a potential therapeutic agent in patients with autism. We characterized the human secretin locus to determine whether mutations in this gene might play a role in a fraction of autism patients. While the secretin gene (SCT) was not found to be mutated in the majority of autistic patients, rare heterozygous sequence variants were identified in three patients. We also investigated length variation in a variable number of tandem repeats (VNTR) immediately upstream of SCT and found no significant differences in length between patients with autism and normal controls. SCT is located on 11p15.5, adjacent to DRD4 and HRAS. This region has been reported to be associated with both autism and attention deficit hyperactivity disorder (ADHD). Although imprinting is a characteristic of some genes in the vicinity, we could find no evidence for methylation of SCT in lymphoblast cells from patients or control individuals.