The records of 102 children with inflammatory bowel disease (44 with ulcerative colitis, 58 with Crohn's disease) were reviewed for evidence of joint disease unassociated with erythema nodosum. Thirteen children had arthritis, four had ulcerative colitis, and nine had Crohn's disease. Arthritis tended to be pauciarticular; ankles, knees, elbows and hips were most commonly affected. In three patients arthritis preceded bowel symptoms, in two the onset of arthritis and bowel disease was concurrent, and in eight arthritis appeared after the onset of bowel symptoms. The relationship between arthritis and specific features reflecting activity and severity of the bowel disease was examined in detail. Twenty-one attacks of arthritis, ranging in duration from two days to 12 weeks (mean, 31 days) were documented. Thirteen attacks occurred when the bowel disease was symptomatic; nine occurred within one month of a flare of the bowel disease. Most exacerbations of bowel disease in patients who had arthritis were unaccompanied by joint complaints. None of the features reflecting activity or severity of the bowel disease was more common in patients with arthritis than in those without arthritis.