Ten days after finishing a course of oral amoxicillin for streptococal pharyngitis, a 38 year old woman developed a fever, arthralgias, and persistent tender red plaques on her trunk and extremities. Many of the plaques were studded with vesicles, bullae, and pustules, and some appeared along cat scratch marks and other areas of trauma typical of the Koebner or isomorphic phenomenon. Laboratory studies showed a leukocytosis with marked neutrophilia and an erythrocyte sedimentation rate of 80 mm/hr. Antistreptodornase antibodies were also elevated. A skin biopsy of a plaque on her arm showed a dense superficial neutrophilic infiltrate in the dermis extending into the epidermis consistent with Sweet syndrome. She defervesced, the rash improved, and other symptoms resolved shortly after starting a tapering course of oral prednisone beginning at 60 mg/day.