Manual dilatation of the anus was carried out on 50 unpremedicated outpatients under propanidid, nitrous oxide, and halothane anaesthesia with E.C.G.monitoring. About half of the patients received intravenous atropine with the propanidid. The operation induced a variety of changes in heart rate but in the whole experiment only two isolated cardiac arrhythmic complexes were seen-a single defect of conduction and a solitary ventricular extrasystole. Changes in rate were not modified by atropine. It is concluded that manual dilatation of the anus is a safe procedure when carried out under the anaesthetic described and that prior medication with atropine is not necessary. This work supports the view that propanidid protects patients from most abnormalities of heart action which result from intense visceral stimulation.