A review of two years' experience with heparin therapy administered intravenously in a coronary care unit population revealed that elderly women were particularly susceptible to bleeding episodes. Congestive heart failure may have been a contributing factor. Bleeding into the hip and groin occurred with unusual frequency and may have been due, in part, to parenteral administration into the buttocks of medications other than heparin. The first warning of bleeding occurred on an average of 48 hours before overt evidence of bleeding was noted.