Abstract: Objective To observe the dynamic changes of plasma adrenomedullin (ADM) levels and the effect of enalapril intervention in diabetic rats. Methods Fifty-two wistar rats were grouped into 1-and 3-month groups (7 each), both including a control and a streptozotocin-induced diabetic group. The 5-month group was divided into control, diabetic and enalapril-treatment diabetic groups (8 each, the last group receiving oral enalapril treatment at the daily dose of 2 mg/kg from the first to the fifth month after diabetes inducion). Blood samples were collected from the heart of the rats at the end of 1, 3 and 5 months for determination of plasma ADM concentrations radioimmunoassay. Results Plasma ADM levels were significantly higher in diabetic rats than in the corresponding control rats in 1-and 3-month groups. ADM levels in the diabetic rats of 5-month group were significantly decreased in comparison with that of 1-and 3-month groups. In 5-month group, plasma ADM levels of enalapril-treated diabetic rats elevated significantly in comparison with that in the control rats and the diabetic rats without enalapril treatment. Conclusion ADM may play an important role in the pathophysiology of diabetes.