NIDDM has been postulated to be a component of a more generalized metabolic syndrome, Syndrome X, caused by insulin resistance. Although the components of the syndrome include glucose intolerance, hypertension, increased TG, and decreased HDL cholesterol, their relationship to insulin resistance and/or hyperinsulinemia is controversial. Recent investigations have shown racial differences in the relationship between insulin resistance and BP in nondiabetic populations. We assessed the relationship between insulin resistance and the other components of the syndrome in 37 black men and 53 black women with NIDDM. Insulin sensitivity was determined by measuring glucose disposal with the euglycemic insulin clamp technique with a 1 mU.kg-1.min-1 insulin infusion. We also determined fasting lipid profiles and BP. In this group of black men and women with NIDDM, 30% were insulin sensitive, and 70% were insulin resistant. No correlation existed between insulin sensitivity and sBP or dBP in either sex. Fasting serum TGs were inversely correlated with insulin sensitivity for both men (r = -0.401, P = 0.02) and women (r = -0.366, P = 0.008). Serum HDL cholesterol was highly correlated with insulin sensitivity for men (r = 0.421, P = 0.01) but not for women (r = 0.071, P = 0.62). Fasting serum TG levels and serum HDL-cholesterol levels were highly correlated in an inverse relationship in men (r = -0.368, P = 0.03), but not women (r = -0.199, P = 0.17). In summary, BP does not correlate with insulin resistance in blacks with NIDDM. Normal insulin sensitivity occurs in 33% of black men and 25% of black women with NIDDM.(ABSTRACT TRUNCATED AT 250 WORDS)