This study investigated the effect of antihypertensive therapy with lisinopril on plasma cholesterol concentration and erythrocyte catalase activity in hypertensive patients. We observed, for the first time, significant inverse correlations between systolic blood pressure (BP) and erythrocyte catalase activity and between diastolic BP and erythrocyte catalase activity. Plasma total and low density lipoprotein (LDL) cholesterol as well as triglyceride levels were similar between baseline and 1-, 3-, and 6-month treatment values in the same patients; however, systolic and diastolic BP levels were expectedly reduced after the therapy. Thus, there was no association between BP and lipid-cholesterol metabolism. These findings confirm antihypertensive effect of lisinopril and suggest that erythrocyte catalase is involved in BP control in hypertension and antihypertensive therapy.