Neurexins are presynaptic membrane cell-adhesion molecules which bind to neuroligins, a family of proteins that are associated with autism. To explore the possibility that structural variants in the neurexin alpha genes predispose to autism, the coding regions and associated splice junctions of the neurexin 1alpha gene were sequenced in 116 Caucasian patients with autism and 192 Caucasian controls. Five ultra-rare structural variants including a predicted splicing mutation were found in patients with autism and absent in 10,000 control alleles. Only one ultra-rare structural variant was found in controls (5/116 vs. 1/192; P=0.03, Fisher's exact test, one-sided). In the context of all available data, the ultra-rare structural variants of the neurexin 1alpha gene are consistent with mutations predisposing to autism.