To examine the impact of family history of diabetes mellitus 2 (DM 2) on insulin sensitivity and secretion in lean women with polycystic ovary syndrome (PCOS). Thirteen healthy women (C), 14 PCOS without family history of DM 2 (FH-) and 8 PCOS with family history of DM 2 (FH+) were examined using euglycemic hyperinsulinemic clamp and an arginine secretion test (insulin and glucagon at fasting glycemia (AIR(FG) and AGR(FG)) and at hyperglycemia (AIR(14) and AGR(14)). FH+ women were more insulin resistant than FH- with lower insulin sensitivity index corrected per lean body mass (p 0.05). They had significantly higher triglycerides (p 0.05) and lower HDL-cholesterol (p 0.05) than C or FH- women. Concerning insulin secretion, AIR(FG) was increased in FH+ women comparing FH- women (p 0.05). Disposition indices derived from AIR(FG) or AIR(14) and insulin sensitivity index did not differ between FH+ or FH-. Thus, women with PCOS with the concomitant family history of DM 2 have lower insulin sensitivity than healthy control women. Insulin resistance observed in these women with PCOS is compensated by increased insulin secretion.