Sodium, potassium and water distribution, central hemodynamic parameters, and plasma renin activity and aldosterone levels were examined in 48 patients with stable essential hypertension, including 10 males and 11 females with hypertensive crises aggravating the course of the disease, and in 18 controls. The individuals showing signs of heart and renal failure were excluded from the analysis. In female patients, the crise pattern of the disease was associated with marked changes of sodium metabolism, namely, raised extracellular fluid and plasma sodium levels, the patients with the crises having a more severe course of the disease, with higher, as compared to those of crises-free patients, total peripheral resistance and lower cardiac output values. In female patients with the crises, plasma renin activity was reduced 3.3-fold, while aldosterone levels remained unchanged, as compared to the levels of crises-free women. A direct correlation was demonstrated between the recurrence of the crises and total peripheral resistance. Causes of sodium retention in female patients with the crises are discussed.