Vasodilator drugs lead to secondary baroreflex mediated chronotropic effects. The aim of the present study was to evaluate long term therapy with nicardipine, a calcium antagonist, on exercise performance and autonomic nervous system activity. Nicardipine was administered to 10 untreated mild-moderate essential hypertensive patients. Isometric (hand grip) and dynamic (bicycle ergometer) exercise, and parasympathetic activity evaluated on the basis of Variation of Heart Period (VHP) during regular breathing were determined. Blood pressure was significantly lowered by nicardipine both supine and standing (p less than 0.001). Heart rate did not change. The increase of blood pressure during isometric and dynamic exercise was similar both before and during nicardipine. The increase of heart rate during dynamic exercise was lowered by nicardipine. The lack of basal supine and standing chronotropic activation and the smaller increase of heart rate during bicycle ergometer could be explained by the observed increase in parasympathetic activity, as indicated by the rise of VHP.