A 50-year-old woman developed an acute febrile dermatosis on two occasions concurrently with recurrent Crohn's disease of the colon. Based on the presence of painful erythematous plaques on both hands and forearms, on the leukocytosis with excess bands in peripheral blood, on the histology showing dermal infiltration by mature granulocytes, and on the prompt response to steroids, the diagnosis was made of Sweet's syndrome associated with Crohn's disease. Sweet's syndrome is thought to be a hypersensitivity reaction that leads to parainflammatory (e.g., infections, autoimmune disorders, vaccinations) and paraneoplastic (myeloproliferative disorders, solid malignancy) associations, with a frequency of 10-30%. The association of Sweet's syndrome with Crohn's disease is very rare, but the gastroenterologist should readily differentiate it; it is important to be aware that such patients may have a nonspecific elevated activity index owing to the underlying dermatosis.