A conference sponsored by the NHLBI and the University of Pittsburgh in 1984 comprehensively reviewed the concept of reactivity, its measurement, and its hypothesized relationship to a disease process. The value of CVR is that it provides an estimation of the changes in cardiovascular function in response to the challenges of daily life, and thus may serve as a better marker or predictor of cardiovascular disease risk than the usual 'casual' measurements. Essential hypertension appears to be a multi-factorially determined disorder, whose etiology encompasses different elements for different individuals. Physiological changes induced by excessive cardiovascular reactivity are among the mechanisms suggested to account for the transition from borderline to established hypertension. In this model, episodic cardiovascular activation elicited by behavioral challenges leads to autoregulatory adjustments culminating in elevated blood pressure. An alternative interpretation is that both elevated CVR and elevated blood pressure are reflections of underlying nervous system pathology. Prospective studies, using appropriate behavioral designs and a standardized protocol to assess cardiovascular reactivity could distinguish between these alternatives.