Rectus sheath hematomas are uncommon and are being caused by the injuries of the epigastric vessels and the rectus muscle. They are usually located infraumblically and often misdiagnosed as inflammatory diseases or tumours of the abdomen. We present a 70-year-old woman who had complaints of severe abdominal pain on the left side, nausea and vomiting after heavy lifting. Rectus sheath hematoma was detected by abdominal ultrasonography and computerized tomography. The patient recovered uneventfully after bed rest, intravenous fluid replacement, blood transfusion and analgesic treatment. Computerized tomography must be chosen for definitive diagnosis. Ideal treatment is conservative.