Enoxaparin is a low-molecular-weight heparin used for prophylaxis against deep venous thrombosis. Indications include hip and knee replacement surgery, risk of deep venous thrombosis during abdominal surgery, and prevention of ischemic complications of unstable angina and non-Q-wave myocardial infarction. Its efficacy in the prevention of the above complications has been previously studied; however, the liberal use of enoxaparin is not without incident. Complications of enoxaparin include hemorrhage, thrombocytopenia, and local reactions. Since 1993 there have been more than 40 reports of epidural or spinal hematoma formation with the concurrent use of enoxaparin and spinal/epidural anesthesia or spinal puncture. Herein reported are two cases of abdominal wall hematomas in patients receiving prophylaxis with enoxaparin. Both patients sustained an unexplained fall in the hematocrit and abdominal pain. A CT scan confirmed the diagnosis. One patient recovered uneventfully; however, the other patient, on chronic hemodialysis, became hemodynamically unstable and hyperkalemic and sustained a fatal cardiac arrhythmia. An extensive review of the literature revealed no similar cases of abdominal wall hematomas associated with enoxaparin although other complications, including spinal and epidural hematomas, psoas hematomas, and skin necrosis have been reported. The extended use of enoxaparin as an anticoagulant requires the physician to be vigilant of these rare complications. Bleeding can occur at any site during therapy with enoxaparin. An unexplained fall in the hematocrit or blood pressure should lead to a search for a bleeding site.