In a randomised study on 20 healthy female subjects we compared the effect of two low-dosage antiovulants containing gestodene or desogestrel on ovarial and adrenal function and on fatty metabolism. Both antiovulants produced a moderate inhibition of gonadotropin secretion and a marked suppression of serum levels of oestradiol, testosterone and free testosterone; there was a strong increase in sex hormone-binding globulin, and an increase in cortisol--probably due to the increase on corticosteroid-binding globulin--and a continuous drop in dehydroepiandrosterone S. In all cases there was no significant difference between the effect of both preparations. Whereas there was no change in total and LDL cholesterol, total phospholipids and VLDL triglycerides, there was a significant increase in the concentrations of apolipoprotein B, total triglycerides, the cholesterol and phospholipid properties of VLDL as well as of all components of HDL. The LDL triglycerides were also elevated, whereas the LDL phospholipids dropped. On the whole the changes in lipid metabolism, which indicate a certain predominance of the oestrogen effect, were low. However, it became that the duration of intake exercises considerable influence.