The efficacy of pharmacologic doses of steroids in the treatment of septic shock was evaluated using a laboratory model. The model produced a septic insult of gradual onset followed by a rapid progression, allowing for the evaluation of postcontamination therapeutic regimens. In Sprague-Dawley rats, the cecum was ligated distal to the ileocecal valve and doubly punctured. Control animals (n = 41) received no postoperative therapy. Mortality was 37 per cent at 24 hours and 90 per cent at 48 hours. Approximately 25 animals were assigned to each of five experimental groups. Pharmacologic doses of methylprednisolone at four and eight hours postoperatively did not alter survival. Short-term gentamicin (STG) at four and eight hours improved early survival, which then declined to control values. Addition of steroid to STG had no effect. Long-term gentamicin (LTG) administered through the third postoperative day produced significant increased survival over controls throughout the study. Pharmacologic doses of steroid at four and eight hours added to LTG resulted in a significant increase (P less than 0.05) in survival rate over the treatment with LTG alone.