I was surprised to read in your leading article on this subject (November 20, p. 1216) the statement that''pharmaceutical companies seem to be preferring 17alpha-hydroxyprogesterone derivatives in oral contraceptives.'' The last surviving product on the British market containing 1 of this variety of progestogen (megestorl acetate) disappeared when Volidan was withdrawn in 1975. The 22 combined pills (containing 50 mcg of estrogen or less) and the 4 progestogen-only preparations currently available in this country all rely on 19-nortestosterone derivatives. Of these, norgestrel has no inherent estrogenicity and yet when as little as .15 mg is combined with only 30 mcg of ethinyl estradiol it provides the degree of reliability quoted in your article. Editors's note: Our leading article was, perhaps, misleading on this point. Certainly all the combined oral contraceptives currently available in Britain use 19-nortestosterone derivatives for their progestogen component - and there are good commercial and clinical reasons for that choice. However, a switch to 17alpha-hydroxyprogesterone derivatives would make it easier to calculate the estrogen content of contraceptives without having to make allowance for a variable amount of metabolic conversion from nortestosterone. There is, we believe, a resurgence of interest in that alternative, though no new formulations are yet on trial.