We compared serum lipoproteins and clinical factors between non-insulin dependent diabetic (NIDDM) patients with (n=50) and without (n=108) ischemic heart disease (IHD). The patients with IHD were older and had longer durations of diabetes mellitus than those without IHD. Serum lipids, lipoproteins and apoproteins were comparable between the two groups. The relative distribution of TG in the VLDL fraction was significantly higher, while the relative distribution of TG in the LDL fraction and Apo E/VLDL ratio were significantly lower in patients with IHD than in those without IHD. Multiple regression analysis also indicated that these factors were significantly related to the presence of IHD. It was suggested that hypertriglyceridemia, especially an increase in the relative distribution of TG, plays an important role in the development of IHD in patients with NIDDM.