The preoperative differential diagnosis of injuries to the abdominal viscera depends on detailed correlation of physical and laboratory findings at the time of admission with the findings of the surgeon at laparotomy. Analysis of 338 such cases showed that the most distinct effect was the leukocytosis that followed rupture of the liver or spleen by blunt trauma. The average of 23,890 white blood cells per cubic millimeter seen in liver injuries and 19,050 in blunt trauma to the spleen was higher than that caused by gunshot or stab wounds to these viscera and also higher than that following trauma of any sort to other abdominal viscera. The data on systolic blood pressure and hemoglobin concentration, though valuable in evaluating the condition of the patient, did not lead to comparable generalizations. A total leukocyte count of 15,000 or more per cubic millimeter justifies the suspicion of ruptured liver or spleen if other findings are compatible with that diagnosis.