Peridural analgesia was combined with the respiratory-stimulant effect of doxapram for intermittent hyperinflation of the lungs to reverse early postoperative (PO) hypoxemia following inhalation anesthesia for upper abdominal operations. Twenty unpremedicated men undergoing upper abdominal operations were studied for 5 hours in the recovery room. Ten of these patients received doxapram plus peridural analgesia; the other 10, doxapram plus morphine analgesia. Rectal temperature, PaO2, PaCO2, respiratory rate, exhaled minute ventilation (VE), tidal volume (VT), and blood pressure and pulse were measured. The mean increase from control for VE was 9.6 L/min and for VT, 356 ml/breath during doxapram therapy for the morphine group. Corresponding values for the peridural group were 14.4 L/min for VE and 660 ml/breath for VT. Mean PaO2 for the morphine group decreased significantly from the corresponding preoperative value (p less than 0.005). Lack of significant change between preoperative and PO values for PaO2 for the peridural group would indicate that under the conditions of this study, early PO hypoxemia can be reversed by the combination of peridural analgesia with doxapram therapy.