Seventy patients had exploratory laparotomy after blunt abdominal trauma in 1969 at Harbor General Hospital. Forty-eight (69%) had preoperative peritoneal lavage. Seeking to evaluate the safety and sensitivity of this technique, the results have been summarized. We conclude that (1) Very small amounts of blood can yield a positive result. Two false positives resulted from puncture site bleeding. (2) Most positive results are unequivocal (67%). (3) Attention to the procedural details outlined should aid to minimize complications. (4) The complication rate of properly conducted diagnostic peritoneal lavage is sufficiently low to warrant continued enthusiastic use of this technique when indicated.