Two patients each with a two-year history of chronic ulcerative colitis developed, over a 24- to 48-hour period, painful pustules involving the skin and oral mucosa. The pustular eruption was associated with a severe exacerbation of the colitis. Culture of the lesions and of the blood failed to reveal an infectious cause for the eruption. Histologic study of a pustule in case 2 revealed suppurative folliculitis. The lesions subsided rapidly in case 1 when intravenous hydrocortisone and intravenous and intramuscular antibiotics were administered, and further resolution occurred after colectomy. A similar rapid resoultion of the pustules occurred in case 2 after initiation of treatment with intramuscular cortisone acetate and antibiotics and with colectomy. This pustular eruption may represent a variant of pyoderma gangrenosum.