Peritoneal lavage is an invaluable adjunct in the evaluation of abdominal trauma. Of 780 abdominal trauma patients in a prospective study, 685 underwent percutaneous peritoneal lavage. RBC counts in the effluent above 50,000/mm3 corresponded well with findings at exploration; however, two thirds of the patients having counts between 20,000-50,000/mm3 had serious injury at celiotomy. The data suggest the need for a reappraisal of lavage criteria for operation.