High density lipoprotein cholesterol and apolipoprotein A-I levels were measured in about one thousand 32-33-year-old women taking part in a cardiovascular screening programme. After corrections for differences in smoking habits and use of alcoholic drinks women on various types of steroid contraceptives had widely different levels of high density lipoprotein cholesterol and apolipoprotein A-I. Lowest levels were found in users of lynestrenol-containing minipills (progestagen-only pills) and highest levels in lynestrenol-containing minipills. Of the two commonly used low-estrogen pills ("sub-50 pills") one type (containing levonorgestrel) was associated with elevated and the other (containing lynestrenol) with depressed levels of high density lipoprotein cholesterol and apolipoprotein A-I as compared with the reference group of non-users of oral contraceptives.