The rectus sheath hematoma is a generally rare disease, however the frequency of occurrence has increased with introduction of anticoagulant therapy. It almost always mimics the symptoms of acute abdomen. In 7 out of 14 cases, which we observed, an anticoagulant therapy was administered. During this therapy 5 rectus sheath hematomas occurred spontaneously. In the remaining 2 patients severe coughing attacks were reported additionally. The case histories of the other 7 patients included 3 patients with bronchitis, 2 patients with trauma and 2 patients without a relevant history ("spontaneous"). The correct diagnosis of rectus sheath hematoma could primarily be revealed by sonography in 8 of 14 patients, after which an appropriate therapy followed. In 6 patients a laparotomy was performed, because rectus sheath hematoma was not considered. The correct diagnosis was found intraoperatively as a surprising assessment. By inclusion of rectus sheath hematoma in the differential diagnosis of acute abdomen and the verification by sonography an emergency laparotomy because of a false diagnosis in the often severe ill patients can be avoided in favour of a minor and more appropriate procedure.