In anaesthetized dogs, stellate ganglion blockade led to a moderate disturbance in left ventricular diastolic function. We investigated the effect of a left-sided block, following injection of 10 mL bupivacaine 0.5%, on echocardiographic variables of ventricular function in eight otherwise healthy patients with sympathetically mediated pain syndromes. After the blockade, heart rate (control: 66±3 (mean± SEM), block: 64± 3 min−1) and mean arterial blood pressure (88.5±6.0 vs. 84.0±8.1 mmHg) were unchanged, but afterload decreased (end-systolic meridional wall stress; 69.6±9.9 vs. 59.8±7.1, P<0.05). Stroke volume increased from 71.2±8.1 to 79.6±7.4 mL, P <0.05. Variables of systolic function were unchanged, but relaxation was prolonged (isovolumic relaxation time; 71±5 vs. 81±4 ms, P<0.05). In patients who were ASA I, there was a small impairment in echocardiographic variables during ventricular relaxation after a left stellate ganglion blockade. This small effect did not compromise ventricular function, and the heart responded with a small stroke volume increase to the simultaneous afterload reduction.