The present study was undertaken to investigate the efficacy of a new, highly purified (purity greater than 91%), ethyl esterification product from natural eicosapentaenoic acid (EPA-E, C20:5 omega 3) in patients with type II diabetes mellitus (NIDDM). Hemodynamic changes were assessed at the level of the dorsalis pedis artery using an ultrasonic color Doppler duplex system before and after oral administration of EPA-E at a dose of 1800 mg/day for 48 weeks. The cross-sectional area of the dorsalis pedis artery increased significantly from 2.5 +/- 0.2 to 3.9 +/- 0.4 mm2 (48 weeks, mean +/- SE, p < 0.05). Moreover, EPA-E improved the clinical symptom (coldness, numbness) as well as the vibration perception threshold sense of the lower extremities [from 32.1 +/- 8.5 to 16.1 +/- 4.8 (48 weeks) microns]. A significant decrease of serum triglycerides was also noted by EPA-E administration. Furthermore, significant decrease of the excretion of albumin in urine [from 24.4 +/- 3.3 to 13.9 +/- 1.8 (48 weeks) mg/g.Cr, p < 0.05]. The results of this study suggest that EPA-E has significant beneficial effects on diabetic neuropathy and serum lipids as well as other diabetic complications such as nephropathy and macroangiopathy.