PIP: Reports regarding the question of whether oral contraceptive (OC) use enhances the risk of cancer or one of several serious cardiovascular disorders, i.e., thromboembolic disease, stroke, and myocardial infarction are reviewed. In 1974 the Royal College of General Practitioners (RCGP) issued an interim report of a large prospective study involving 46,000 women. The study found a 5-fold increase in the risk of deep venous thrombosis among women taking OCs. Laboratory studies have tried to establish a direct causal relationship between OC use and altered hemostatis. In review of these studies, Bingel and Benoit reported an increased incidence of thromboembolism in OC users with blood group A. Other hemostatic alterations in OC users were also noted. Other investigators have examined the effect of OCs on antithrombin 3. In 1 study, the inhibitory activity of antithrombin 3 on factor X was significantly reduced among 57 women using the combined OCs, but there was no substantial difference in the quantity of antithrombin 3 in these women as compared with 48 women in the control group. In 1 retrospective case control study of 60 surgical patients with complications of pulmonary embolism or venous thrombosis, the risk of postoperative thromboembolism was 6.7 times greater in OC users than in 97 well matched surgical controls. The RCGP study showed that the risk of cerebrovascular disease in women using OCs was 4 times greater than in nonusers. This finding was substantiated by the Boston-based Collaborative Group for the Study of Stroke in Young Women, which observed a 2-fold increase in risk for all types of stroke among OC users. Several studies have demonstrated that serum lipids are higher in women who use OCs than in those who do not, with estrogen being implicated as the cause of the elevation. Other studies have attempted to link serum lipid elevations to myocardial infarction, but the association is unclear. Both epidemiological and laboratory studies have implicated OCs in the genesis of essential hypertension. Several studies have examined mortality trends associated with OC use. In 1 analysis of data from 21 countries, women between 15 and 44 years of age were found to have a 3-fold to 5-fold increase in cardiovascular mortality that was associated with OC use. The principle evidence that suggested a possible link between OCs and breast carcinoma derived from experiments in laboratory animals. There is no conclusive evidence that OCs cause breast cancer in humans. The association between OC use and endometrial cancer is also inconclusive at this time. A marked increase in the incidence of hepatic adenomas among OC users has also been noted recently. The following other effects associated with OC use are reviewed briefly: glucose tolerance tests; birth defects; gallbladder disease; postpill amenorrhea; laboratory tests; and drug activity. Absolute and relative contraindications for OC use are listed.