This study investigated the hemodynamic effects of the D-isomer of sotalol in open-chest rats and compared this to the action of the L-isomer and the racemic DL-sotalol. Hemodynamic and additional isovolumic maximum measurements were registered at the end and 5 minutes after an intravenous infusion period of 7 minutes. DL- (1 and 2 mg/kg) and L-sotalol (2 mg/kg) caused a significant reduction in the heart rate and in the indices of contractility during and after infusion. D-sotalol (2, 4, and 8 mg/kg), however, decreased the contractility only transiently after very high doses at high plasma concentrations. Thus, while the effects of the beta-blocking L-isomer were comparable to those of DL-sotalol, only a slight and transient hemodynamic action of comparable doses of D-sotalol was found. These findings may be of significance for the proposed use of the D-isomer as a class-III antiarrhythmic agent.