Peritoneal lavage was carried out in 830 patients with blunt abdominal trauma. Positive as well as negative results proved to be very reliable (98% and 99.5% accuracy). With weakly positive findings, however, significant internal injuries were present in only half of the cases. If compared to circulatory parameters, laboratory investigations and clinical evaluation of the abdomen at the time of hospitalization, peritoneal lavage proved to be the superior aid in making a decision to operate. It therefore should be used routinely--even in smaller hospitals--especially before transferal of a patient to a distant special surgical center.