Collagenous colitis, a disorder characterized by increased subepithelial collagen deposition associated with an inflammatory infiltrate in the lamina propria, has been reported infrequently in children. An 8-year-old girl with collagenous colitis is described who presented with chronic watery diarrhea and abdominal pain. Biopsy specimens of the colonic mucosa showed the pathological features of collagenous colitis. The patient's symptoms resolved following corticosteroid therapy. Collagenous colitis should be considered in the differential diagnosis of children with chronic diarrhea.