The effects of an intramuscular injection of pethidine (1.5 mg/kg) plus atropine 0.5 mg, or pethidine (1.5 mg/kg) plus atropine 0.5 mg plus metoclopramide 10 mg on the lower oesophageal sphincter pressure have been studied manometrically in human volunteers. The mean barrier pressure in the former group was significantly lower than the baseline for the 75 minutes studied. In the latter group the mean barrier pressure was significantly lower than the baseline value for the first 45 minutes only of the study. The addition of atropine 0.5 mg to pethidine 1.5 mg/kg further lowers the barrier pressure when compared with the depression seen with pethidine alone in a previous study. While the addition of intramuscular metoclopramide to the mixture of pethidine and atropine fails to return the mean barrier pressure to the baseline value, it does raise the mean barrier pressure to a level which is probably above the opening pressure of the lower oesophageal sphincter.