The effect of premedication with morphine and anticholinergic dugs on absolute and interpeak latencies of brain stem auditory evoked potentials was studied in thirty patients. Two commonly used anticholinergics, glycopyrrolate and scopolamine, given in combination with morphine were studied. Patients premedicated with morphine alone served as a control group. No significant change in either absolute or interpeak latencies was noted in patients premedicated with either morphine alone or morphine and glycopyrrolate. Results in patients premedicated with morphine and scopolamine are inconclusive because of large intersubject variability.