The purpose of this study was to investigate the effects of L-carnitine administration on lipid metabolism in streptozotocin-induced diabetes. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg/kg b.w.) and was confirmed by determination of urinary glucose secretion. Diabetic rats in the three L-carnitine treated groups were given L-carnitine, 50(D5O), 100(D100) and 200 (D200) mg/kg body weight, by subcutaneously every other day for four weeks, while animals in normal (N) and diabetic (DM) groups for control received saline by the same method. The daily weight gain was not different between normal and diabetic rats, but daily dietary intake was significantly higher in diabetic rats than in normal rat. Diabetic rats had a significantly lower carnitine concentration in both serum and liver compared to normal rats. Total carnitine concentration in serum was increased dose dependently upon carnitine administration, but statistic significance was shown only in D200 group. Diabetic rats had significantly higher serum triglyceride and cholesterol concentrations compared to normal rats. However there were no significant differences in liver L-carnitine administration to diabetic rats significantly decreased serum triglyceride but not cholesterol concentrations. In liver, triglyceride and cholesterol concentrations were not attired by L-carnitine administration. These results indicated that streptozotocin induced-diabetic rats have decreased carnitine and increased lipid concentrations compared with normal rats. Also it indicated that L-carnitine administration has an effect on the normalization of serum triglyceride concentrations in diabetic rats.