Intravenous glucose tolerance tests (IVGTT) with simultaneous assessment of plasma insulin and analyses of the fatty acid composition of serum lecithin and cholesterol esters were performed in 11 women with previous gestational diabetes before and repeatedly during 6 months’ administration of a low-dose progestogen (lynestrenol = LYN). 8 of these women were also followed in an identical manner during 6 months of nonhormonal contraception (intrauterine device = IUD) and additionally 6 of these women were followed also during the use of a combined oral contraceptive (OC) (ethinyl estradiol + lynestrenol = EE + LYN). LYN did not alter the IVGTT or plasma insulin but decreased the proportion of polyunsaturated fatty acids (PUFA) in serum lecithin (p < 0.01) and cholesterol esters (p < 0.01) where oleic acid was reciprocally increased (p < 0.05). After 6 months’ use of IUD, on the other hand, thek value of IVGTT increased by 45% (p < 0.01) without significant changes in plasma insulin. In both lecithin and cholesterol ester PUFA increased (p < 0.05) and cholesterol ester oleate decreased (p < 0.01); i.e., virtually the reversal of the changes seen during LYN administration. The combined OC, EE + LYN, caused a decrease of the k value by 27% (p < 0.05) which was apparent even when compared to the effects of LYN alone. EE + LYN also increased (p < 0.05) lecithin palmitate and decreased stearate (p < 0.05) and had a concomitant tendency to lower PUFA and increase oleic acid in both lecithin and cholesterol esters. These results indicate that LYN has little influence on the glucose tolerance in women predisposed to diabetes but may provide poorer conditions for dietary treatment of subclinical diabetes than do nonhormonal IUDs. The combined OC, EE + LYN, on the other hand, promptly diminishes glucose tolerance and may also have an unfavorable influence on liver metabolism.