The effects of the use of oral contraceptives on serum lipids and blood pressure were studied among young women who participated in a longitudinal survey of risk factors for coronary heart disease (CHD) in the Netherlands. Fifty-three participants, ages 14 to 24 years, initiated oral contraceptive use during follow-up to the primary study on CHD. They continued oral contraceptive use for at least 2 subsequent years. From 53 age-matched control subjects, who did not use oral contraceptives, data were obtained for the same follow-up period. Women using oral contraceptives showed a significantly greater rise in serum total cholesterol levels than did the reference subjects (14 mg/100 ml/2 year vs 4 mg/100 ml/2 year; 95% confidence interval of the difference was 0.1 to 19.6). The increase in systolic blood pressure (4.7 mm Hg/2 year vs 2.1 mm Hg/2 year; 95% confidence interval of the difference was -1.8 to 6.9) did not differ between the groups. These findings suggest that oral contraceptive use may be associated with an enhanced rise in total cholesterol during adolescence.