Forty patients with neuromuscular disorders of the gastrointestinal tract were evaluated histologically and radiologically. Eighteen patients with progressive systemic sclerosis had predominant circular muscle thinning and fibrosis. Visceral myopathy (11 patients) was characterized by vacuolar degeneration of the smooth muscle cells with thinning and fibrosis typically affecting the longitudinal layers. Visceral neuropathy (five patients) had degeneration of myenteric plexus neurons with various patients having intranuclear inclusions, Schwann cell proliferation, or inflammatory cell infiltration. Radiologically, these syndromes had diffuse abnormalities of gastrointestinal motor function manifested by small and large intestinal dilatation, esophageal hypomotility (progressive systemic sclerosis and visceral myopathy), or disordered hypercontractility (visceral neuropathy). Marked duodenal enlargement typified visceral myopathy, and although all types may have dilated small intestine, only progressive systemic sclerosis has packing of valvulae. Colonic sacculations were found in progressive systemic sclerosis, lack of haustrations and increased colonic caliber in visceral myopathy, and hypercontractility in visceral neuropathy. Complete barium contrast examination will assist in differentiation of true obstruction from pseudoobstruction, will define the diffuse nature of the syndrome, and will help establish an accurate diagnosis by identifying features specific for these entities.