Several studies have shown that hyperinsulinemia and insulin resistance are associated with high triglyceride and low high-density lipoprotein (HDL) cholesterol levels. However, previous studies have been cross-sectional, and thus the presence of hyperinsulinemia or insulin resistance could be a consequence of the underlying lipid disorder instead of its cause. Therefore, we examined the relation of fasting insulin level measured in a cross-sectional study in nondiabetic subjects 65 to 74 years old (n = 881) to the risk of developing lipid disorders 3.5 years later. The incidence of the following lipid abnormalities was calculated: hypertriglyceridemia (n = 49/732, incident cases/subjects free of the particular disorder at baseline), high low-density lipoprotein (LDL) cholesterol level (n = 43/696), low HDL cholesterol level (n = 33/708), high apolipoprotein (apo) B level (n = 72/699), low apoAI level (n = 47/711), low serum LDL cholesterol/serum apoB ratio (n = 55/685), and low serum HDL cholesterol/serum apoAI ratio (n = 48/707). Baseline insulin level was not significantly associated with the development of high LDL cholesterol or low HDL cholesterol levels. Baseline insulin was associated with the development of hypertriglyceridemia (odds ratio [OR], 1.64; 95% confidence interval [CI], 1.12 to 2.40; P = .011), high apoB (OR, 1.54; 95% CI, 1.13 to 2.10; P = .006), low apoAI (OR, 1.72; 95% CI, 1.22 to 2.42; P = .002), low LDL cholesterol/apoB ratio (OR, 1.99; 95% CI, 1.36 to 2.90; P < .001), and low HDL cholesterol/apoAI ratio (OR, 1.93; 95% CI, 1.34 to 2.79; P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)