Abstract
A study was performed to find out whether the overall rate of metabolism of oral contraceptives is affected by smoking and whether this explains the increased incidence of cardiovascular disease in users of oral contraceptives who smoke. Plasma ethinyloestradiol and norgestrel concentrations in 311 women using oral contraceptives were similar in smokers and non-smokers. The overall rate of metabolism of contraceptive steroids does not therefore seem to be affected by cigarette smoking.