Skin necrosis is a well-recognized although rare complication of continuous heparin therapy. We report the case of a 66-year-old diabetic woman with end-stage renal failure who received intermittent intravenous heparin during hemodialysis. She developed severe necrotic cutaneous ulcers over both legs, with typical histological findings. Thrombocytopenia never occurred but platelet studies demonstrated enhanced aggregation when heparin was added in vitro. Platelet-aggregating immunoglobulins produced in response to heparin can lead to thrombotic events. Thrombocytopenia usually develops prior to the onset of cutaneous lesions, but as in this case, may be absent. Heparin should be discontinued when the condition is recognized. Unfortunately, a poor outcome is frequently observed.