Alinidine (2.9 +/- 0.7 mg/kg) prevented an adrenaline-induced ventricular arrhythmia in dogs respired with halothane. In ouabain-induced ventricular tachycardia, a cumulative dose of alinidine (15.5 mg/kg) reduced the number of ventricular beats by 91.6 +/- 1.9%. The drug was much less effective in abolishing the ventricular tachycardia 24 h after ligation of a coronary artery, with only a 36 +/- 15% reduction in ventricular ectopic beats after 15.5 mg/kg. The administration of alinidine (0.5-1.0 mg/kg) to anaesthetized dogs with no cardiac arrhythmia reduced sinus node rate with little effect on the response of the node to vagal stimulation.