Rectus sheath hematoma (RSH) is an uncommon condition characterized by abdominal pain and an abdominal wall mass. We reviewed the clinical features, treatment, and outcomes of 126 patients treated for RSH at Mayo Clinic from January 1, 1992, to December 31, 2002. Most patients (64%) were women and the mean +/- SD age was 67.9 +/- 16.5 years. Most patients (69%) were on some form of anticoagulation therapy. The mean international normalized ratio was 2.6 +/- 2.4, and mean activated partial thromboplastin time was 64.2 +/- 42.7 seconds. No patients were pregnant or had a peritoneal dialysis catheter at the time of diagnosis. Approximately half of the patients (48%) had nonsurgical abdominal trauma around the time of diagnosis, with 37 patients (29%) having a cough. The most common presenting signs and symptoms were abdominal pain (84%) and an abdominal wall mass (63%). CT of the abdomen and pelvis was the most commonly used method to establish the diagnosis (83%). Most patients (86%) were successfully treated with symptom management and blood transfusion. Ten patients (7.9%) underwent surgery or endovascular embolization of bleeding vessels, and 2 patients (1.6%) died as a result of RSH bleeding. Although RSH is rarely fatal, the clinician should be aware of important risk factors that lead to RSH including female sex, older age, anticoagulation therapy, and cough or other abdominal trauma. Rapid diagnosis with directed history, physical examination, and CT of the abdomen and pelvis may help decrease unnecessary laparotomy and lead to better triage of patients who present with RSH.