Disorders of cholesterol metabolism were studied in 88 patients with essential or renovascular hypertension, among whom the individual stages of the disease, classified by WHO criteria, were evenly represented. The results were compared with the findings in a group of 87 healthy controls. The following were determined in the plasma: the total (TCH) and free (FCH) cholesterol concentration, triglycerides (TG) and lecithin cholesterol acyltransferase (LCAT) activity, defined as the molar esterification rate (MER). The MER/FCH ratio gave the fractional esterification rate (FER) as the percentage per hour. In evaluation of the whole group of hypertensive patients, the mean TCH values were found to be raised (6.62 as against 6.05 mmol/l, P less than 0.05), but FCH levels were raised more significantly (mean 1.76 as against 1.51 mmol/l, p less than 0.001). With normal MER values, the hypertensive group had a significantly lower mean FER value (5.45 as against 6.27 %/h, p less than 0.001). Mainly patients with stage II and III hypertension accounted for the reduced rate of cholesterol recirculation between plasma and tissues (i.e. the FER value). The findings indicate that a change from stage I to stage II hypertension is accompanied by an increased incidence of lipid metabolism disorders.