Four proved cases of pseudomembranous enterocolitis are presented. In each case either lincomycin or clindamycin (a derivative of lincomycin) was given. Use of such broad spectrum antibiotics appears to be related to the increased incidence of pseudomembranous enterocolitis. Roentgen findings include thickening of the mucosal folds of the small intestine and pseudomembrane formation. When the colon is involved, it may also show thickening and dilatation. With use of contrast medium, expected radiographic findings are edema, shaggy appearance of the mucosa and/or ulceration, findings similar to those seen in inflammatory colitis.