Stroke volume, systolic time intervals and related index variations induced by atropine/neostigmine (AN) (0.75 mg/l mg) decurarization mixture were investigated by non-invasive methods (ECG, phonocardiogram, thoracic impedance) in 15 anaesthetized normocapnic patients in a stable state after induction of anaesthesia and prior to surgical stimulation. Data showed decrease in mean heart rate (HR) (initial value: 82 beats/min; after 10 min: 57 beats/min; P less than 0.001) accompanied by an increase in stroke volume (SV) (initial value: 75 ml, after 10 min: 100 ml; P less than 0.001). No alterations in myocardial contractility were noted with the systolic time intervals (PEP, PEP/LVET, 1/PEP2). Under the conditions of the study, the negative chronotropic effect of AN mixture was not accompanied by a negative inotropic state.