In a 4 year material of closed abdominal injuries consisting of 114 patients, mostly multiple trauma traffic accidents, diagnostic paracentesis with peritoneal lavage was used in 47 cases. The aim of the investigation was to indicate or exclude blood in the abdominal cavity as early as possible and thereby facilitate the priority of treatment and diminish the delay in surgical intervention. The main indication was suspicion of abdominal injury in multiple traumatized, unconscious or shocked patients. The puncture was performed in the emergency room immediately after ordinary lifesaving steps had been taken. If blood was obtained the patients were sent to the operating theatre for laparotomy. If blood was not obtained one litre of an isotonic salt solution was infused and if the returning solution was only slightly blood tinged, the investigation was continued with roentgenographic methods. In our series only two cases were not correctly diagnosed. Diagnostic paracentesis is the most rapid method of demonstrating intraabdominal bleeding, which is found in 90% of all serious intraabdominal organ injuries. In doubtful cases this method must be combined with other diagnostic methods and the patient put under proper clinical observation.