Collagen vascular diseases are known to present with a diverse array of gastrointestinal manifestations. These can be classified as: 1) gastrointestinal damage due to the collagen vascular disease itself; 2) adverse events caused by pharmacotherapies; or 3) gastrointestinal infections following immunosuppression due to corticosteroid (CS) administration. The first group includes lupus enteritis and protein-losing gastroenteropathy in systemic lupus erythematosus (SLE), reflux esophagitis, chronic intestinal pseudo-obstruction, and pneumatosis cystoids intestinalis in systemic sclerosis, amyloidosis in rheumatoid arthritis, bowel ulcer and bleeding in rheumatoid vasculitis and microscopic polyangiitis, and ileocecal ulcer in Behcet disease. In particular, colonic ulcers associated with SLE represent refractory lesions resistant to CS. Analysis of reported cases showing colonic lesions with SLE (22 cases in Japan) revealed that mean duration of SLE was 9.9 years and 77% of colonic lesions were observed in the rectum and sigmoid colon. Half of the patients developed intestinal perforation or penetration, and 6 of the 11 patients with perforation died. The second group includes lesions in the small and large intestine due to nonsteroidal anti-inflammatory drugs (NSAIDs) and CSs, in addition to peptic ulcers. As perforation in CS-treated patients displays relatively high incidence with poor prognosis, careful attention to such complications is needed. The third group includes candidal esophagitis and cytomegalovirus (CMV) enteritis. Prompt diagnosis is required to prevent colonic bleeding and perforation due to CMV.