Evaluation of sympathetic cardiovascular influences has important physiological, pathophysiological and clinical implications. This paper reviews some of the methods employed to measure these influences in man, along with their advantages and disadvantages. The most useful methods appear to be the measurement of plasma noradrenaline (particularly when modified to calculate spillover rate of noradrenaline) and direct recording of sympathetic nerve traffic. With the former, despite the technological advances in measurement, certain methodological problems remain, such as the separation of noradrenaline secretion from clearance. With the latter technique peripheral muscle and skin sympathetic activity can be measured separately but the question of regional vascular variability has still to be resolved. A combination of these two methods may represent the ideal approach. This review considers the complex problems associated with attempts to precisely quantify sympathetic cardiovascular influences in man.