Progressive systemic sclerosis (PSS) is a chronic multisystem disease characterized by excess deposition of connective tissue in skin and internal organs, associated with microvasculature changes and immunologic abnormalities. Involvement of the gastrointestinal tract may occur in 2 stages, a neuropathic disorder followed by a myopathy. Gastric emptying is delayed in 10% to 75% of patients and correlates with symptoms of early satiety, bloating, and emesis. Compliance of the fundus is increased although perception of fullness is normal. Myoelectric abnormalities have been found in some studies. Treatments include metoclopramide, cisapride, and erythromycin. Bleeding from telangiectasias and watermelon stomach is treated endoscopically. Small bowel involvement in PSS occurs in 17% to 57% of patients. The migrating motor complexes are reduced or absent, predisposing to bacterial overgrowth. Malabsorption may also be due to pancreatic insufficiency. Barium enemas demonstrate pancolonic involvement in 10% to 50% of patients with PSS. Wide-mouthed diverticuli, involving all layers of the intestinal wall, are characteristic. Pseudoobstruction may respond to octreotide or prucalopride therapy. Complications include pneumatosis cystoides intestinalis, stercoral ulcerations, and perforation. Fecal incontinence may be due to dysfunction of the internal anal sphincter, a smooth muscle responsible for most of the resting anal sphincter pressure. Anal manometry may show a reduction or loss of the rectoanal inhibitory reflex. Treatments include biofeedback, sacral nerve stimulation, and surgery. PSS involves the gastrointestinal tract from the mouth to the anus. Studies are needed to define effective treatments in these diseases, which cause great morbidity.