A case of agranulocytosis due to dapsone administered for the treatment of acne vulgaris is described. Agranulocytosis has previously been reported after administration of dapsone for other dermatological disorders, leprosy, and prophylaxis against falciparum malaria. The frequency of agranulocytoses when dapsone was used for malaria prophylaxis in United States servicemen in Vietnam was sufficient to result in its withdrawal from use for this purpose. Caution should therefore be exercised in the administration of dapsone for conditions for which less toxic agents are available.