The use of combined oral contraceptives carries a number of well-established major non-contraceptive benefits. Of these, the most important protective effects are suppression of the risk of epithelial cancer of the ovary and cancer of the endometrium. Also of great importance is a reduction in the risk of pelvic inflammatory disease. Needless to say, there are also some established risks of combined oral contraceptives. The most important of these are the vascular ones, comprising effects on acute myocardial infarction, thrombotic stroke, haemorrhagic stroke, and venous thrombosis and embolism. Possible risks which are still under evaluation include an adverse effect on breast cancer and, likewise, on carcinoma of the cervix. More information is needed about both these conditions. A number of authors have provided analyses of varying degrees of complexity in which they have attempted to weigh the benefits and risks of combined oral contraceptives. Results from some of these studies are presented in the paper. On the whole, the findings are reasonably reassuring.