Lipoprotein abnormalities, mainly high very-low-density lipoprotein (VLDL) and low high-density lipoprotein (HDL) levels, increase the risk of coronary heart disease (CHD) in type II diabetic patients. To investigate the relationship between these lipoprotein abnormalities and the postprandial (PP) lipid-clearing capacity, triglyceride (TG) and hormonal levels were determined hourly up to the 4th hour after a mixed meal containing 32.5 g lipids/m2 body surface in 14 treated non-obese type II diabetic patients with adequate nutritional and glycemic control (hemoglobin A1C [HbA1C] < 7%) and in 12 healthy subjects matched for age, sex, and body mass index (BMI). Mean cholesterol levels did not differ between patients and controls, with fasting TG moderately increased in diabetics (140 +/- 70 v 66 +/- 34 mg/dL, P < .01). Whereas fasting TG levels in patients showed a continuous distribution from 55 to 250 mg/dL, postprandial TG clearly identified two different subgroups. A "high-responder" or hypertriglyceridemic subgroup (HTG) showed PP TG levels significantly higher than control levels (290 +/- 62 v 106 +/- 41 mg/dL, P < .001), with higher fasting TG as well (181 +/- 52, P < .01), whereas both fasting and PP TG levels were not different from control levels in the normotriglyceridemic (NTG) diabetic subgroup. The magnitude of the PP triglyceridemic area showed a negative correlation with HDL2 cholesterol (r = .66, P < .001) and a positive correlation with PP HDL2 TG enrichment (r = .80, P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)