The most frequent progestins used as contraceptives with or without estrogens and their effects on glucose tolerance tests and insulin secretion is reviewed. Although changes observed were moderate, they became normal after few cycles of contraceptive use. All combined contraceptives (progestin plus ethynyl estradiol) produced some deterioration of glucose in the tolerance tests and increase in insulin secretion, although these changes were within normal accepted levels. The most notable changes were seen with levonorgestrel, mono or thiphasic, and were minimal with desogestrel or gestodene. No changes occurred with pregnane type compounds, like medroxy progesterone acetate, with no estrogens as the most representative of this group. The determinations of insulin secretion are more reliable if peptide C in plasma is determined, as it is released by the pancreas in an equimolar amount with insulin and is not retained by the liver.