Neural network theory indicates that inadequate expression of nitric oxide will cause narrow cortical neural columns, predicted on theoretical grounds and recently observed in autism. Another recent neuroanatomical finding in autism, early rapid growth of the cerebrum, may also be explained by inadequate expression of nitric oxide. Another long known neuroanatomical abnormality in autism, a reduced number of Purkinje cells in the Cerebellum, may also be caused, or aggravated, by inadequate expression of nitric oxide synthase. Some characteristics, such as motor impairments, sleep problems, deficit in aggression control and reduced nociception, which are not uncommon in autism, have been found in animal studies when nitric oxide synthase has been suppressed.