The authors examined 1132 patients with chronic ulcerative colitis (CUC) seen at the Cleveland Clinic to clarify the relationship between the clinical features of colitis and the incidence and severity of erythema nodosum (EN) and pyoderma gangrenosum (PG). There were 21 patients (2%) with EN and 21 (2%) with PG, both of which affected those with active and extensive colitis. CUC was inactive in only 10% of the EN group and 20% of the PG group; it was left-sided in 20% of the EN group and 15% of the PG group. The mean duration of CUC before the appearance of EN and PG was 5 and 10 years, respectively. Three patients had consulted a dermatologist for PG before a clinical diagnosis of CUC was made. EN and PG recurred in 20 and 33% of cases, respectively. EN appeared almost exclusively on the legs, while PG appeared on various areas of the skin, including the site of ileostomy in one patient. EN was controlled with adequate medical or surgical treatment of CUC, but PG was relatively refractory, requiring specific treatment of its own in 30% of patients. In one case each, EN and PG recurred after subtotal colectomy but had resolved completely after proctectomy. In one patient, PG developed for the first time 1 year after total colectomy. Less than half of EN patients and two-thirds of PG patients ultimately had to undergo colectomy because of bowel disease. No patient required colectomy because of skin lesions.