Recent studies have outlined both the importance and limitations of hemodynamic studies in hypertension. Characterization of any type of hypertension cannot be established in terms of cardiac output or total peripheral resistance alone. It depends more on the way in which various factors (hemodynamics, volume, humoral and neural) interrelate than on disturbances of one factor alone. More studies are needed, not so much of each variable alone as of correlations among those variables, e.g. correlations between humoral factors and hemodynamic characteristics. Further, hemodynamic analyses must be extended beyond calculations of TPR to evaluation of other variables such as magnitude and distribution of intravascular volume, indices of aortic distensibility, of velocity of ventricular ejection and of cardiac performance. Interpretation of the results must also take into account factors such as hemodynamic setting, age of patient, neurogenic stimulation and structural changes amongst others. Careful attention to these variables will allow more accurate conclusions regarding characteristics of different types of hypertension, and patterns of response to therapy. Accurate hemodynamic characterization may help orient diagnosis and a rational choice of treatment in initial stages but specially for evaluation of resistant cases.