Crohn's disease is rarely associated with Sweet's syndrome. We report a 32-year old woman who presented with diarrhea, fever and disseminated erythematous plaques on the arms and the trunk. After colonoscopy with biopsies, Crohn's disease was diagnosed. Skin biopsy showed a dense infiltration of neutrophilic polymorphonuclear leukocytes, establishing also the diagnosis of Sweet's syndrome. Crohn's disease is one of several systemic diseases that may underlie Sweet's syndrome. Treatment with methylprednisolone resulted in a rapid improvement of both gastro-intestinal symptoms and skin lesions.