We analyzed the data from three cross-sectional, population-based surveys in West Germany to evaluate the effect of antihypertensive drug therapy on the level of serum cholesterol in German residents (18,344 males; 19,137 females) aged 25-69 years, after excluding persons with missing values (N = 5529) for any study variable. The data were obtained from the national and regional health surveys that were conducted during the years 1984-1992, within the framework of the German Cardiovascular Prevention Study (GCP). The response rates were between 66.0% and 71.4% for the national surveys and between 65.9% and 83.3% for the regional surveys. Blood-pressure and non-fasting cholesterol measurements were carried out under strictly standardized conditions. Multiple linear regression analysis was used to compare the age-adjusted mean value and prevalence for each of the following study variables: total serum cholesterol, HDL-cholesterol, non-HDL cholesterol, and the ratio of HDL cholesterol/total cholesterol for users and non-users of antihypertensive medications. Antihypertensive medications were reportedly taken during the seven days preceding the survey examination by 7.8% of all males and 10.4% of all females. The beta-blocker type of medication was prescribed most frequently for lowering high blood pressure. In both genders, the strongest age-adjusted effect of an increase in cholesterol level was found for beta-blockers. The difference in the age-adjusted means for non-HDL cholesterol values between users and non-users of beta-blockers was 9.2 mg/dL (p < 0.001) in males and 9.0 mg/dL (p < 0.001) in females. Regression analysis carried out to control for several potential confounders confirmed the results. The findings suggest that mass treatment of hypertension with beta-blockers may be associated with reductions in benefit because of an increase in non-HDL and a decrease in HDL cholesterol levels.