BACKGROUND: As a potent vasoconstrictor isolated from human and porcine vessels, endothelin(Et) is involved in the pathophysiology of various cardiovascular disease. Although the pathophysiological roles of Et in the patient of diabetes needs further investigation, many reports have shown the increased level of Et in the patient of diabetes. Insulin has also been found to play a role in the elevation of Et in vivo and expenmental study. The aim of our study v as not only to estimate the level of Et-1 in the patient of NIDDM and normal subjects but also compare it to the level of plasma insulin, C-peptide and complications of NIDDM. METHODS: Plasma Et-1 levels were measured in 49 patients of NIDDM and 26 normal subjects. All patients of diabetes were divided into 3 groups: group I(patients with no previous treatment), group II (patients with oral hypoglycemic agent), and group lII(patients with insulin therapy). Nerve conduction velocity and ophtha]moscopic examination was done in all pertinent patients, Plasma Et was determined by RIA after extraction with an Prep Sep-Pac C-18 cartilidge. RESULTS: Plasma Et-1 level of the patient of each group and control subject was shown in Table 1. Plasma Et-1 level of the patient of NIDDM was 3.65 +2.05pmol/mL, which was not statistically different from that of control group(2.80+2.07, p=0.105). No significant correlation of plasma Et level with HbAlc, duration of diabetes, triglyceride and cholesterol in the patient of NIDDM was observed(p>0.05). There was not any significant correlation between plasma Et level and complications of diabetes. Such as angiopathy, microalbuminuria and neuropathy. Even through the insulin and Et level seems to he elevated in group III but it is statistically not significant(p>0.05). CONCLUSIONS: Our study suggests that the patient of NIDDM and normal subject statistically show no difference in the level ot Et although there appear slightly high value in the patient group. Any positive correlation is not found between the Et level and those factors such as angiopathy, microalbuminuria and neuropathy. In conclusion futher investigation is needed to clarify the role of Et in the patient of NIDDM.