Plasma lipoproteins and clinical characteristics of non-insulin-dependent diabetic mellitus (NIDDM) patients with (n = 50) and without (n = 108) ischemic heart disease (IHD) were compared. The patients with IHD were older (64 +/- 9 vs 59 +/- 9 years, mean +/- SD, P < 0.01) and had a longer duration of diabetes (14 +/- 9 vs 11 +/- 8 years, P < 0.05). Lipids, lipoproteins and apolipoproteins were comparable in the two groups. The percent distribution of triglycerides (TG) in the very low density lipoprotein (VLDL) fraction was significantly higher (55 +/- 16 vs 50 +/- 17%, P < 0.05). The level of low density lipoprotein (LDL) (33 +/- 14 vs 39 +/- 15%, P < 0.05) and the apo E/VLDL-TG ratio (0.085 +/- 0.045 vs 0.12070.097, P < 0.01), however, was significantly lower in patients with IHD than in those without IHD. Multiple regression analysis also indicated that age, duration of diabetes, percent distribution of TG in VLDL, percent distribution of TG in LDL and the apo E/VLDL-TG ratio were significantly related to the presence of IHD. Hypertriglyceridemia, particularly when characterized by abnormalities of TG distribution, may play an important role in the development of IHD in NIDDM patients.