Combinations of acepromazine maleate, pethidine hydrochloride and atropine sulphate (0.05 mg/kg) or acepromazine maleate and pethidine hydrochloride and acepromazine maleate alone or atropine sulphate (0.1 mg/kg) alone were used to premedicate cats before they were anaesthetised with thiopentone, to investigate their effects on gastric pressure, lower oesophageal sphincter pressure and barrier pressure under anaesthesia. Manometric measurements were made by using a non-perfused manometric technique. The lower oesophageal sphincter pressure was lowest in the cats premedicated with atropine sulphate alone. The difference in barrier pressure between the atropine (0.1 mg/kg) and acepromazine treated cats was highly significant. The risk of gastro-oesophageal reflux appeared to be highest with atropine (0.1 mg/kg) if barrier pressure is used as an indicator of the likelihood of reflux.