BACKGROUND: 1,5-Anhydroglucitol(1,5-AG) has shown to be a better indicator for current status of glycemia than HbA1c or fructosamine. The concentration of 1,5-AG is stable because of large storage pool and metabolic inertness, little influenced by assay variation with broad range of values. Since its reabsorption is competitively inhibited by glucosuria, plasma 1,5-AG decreases with increasing hyperglycemia in diabetic patients. But impairment of renal function may also affect its concentration. We introduced 1,5-AG as a new marker of glycemic control and evaluated the clinical usefulness and the effect of renal function. METHODS: We assayed plasma concentration of 1,5-AG using gas chromatography mass spectrometry in 36 healthy controls, 39 diabetic patients with normal renal function, 19 nondiabetic patients with chronic renal failure. We examined the relationship bewteen 1,5-AG and HbA1c or glucose. Correlation between 1,5-AG and serum creatinine was also investigated. RESULTS: 1,5-AG concentrations were significantly reduced in diabetic patients and in patients with chronic renal failure, compared to healthy controls. 1,5-AG had negative correlation with plasma glucose and HbA1c in healthy controls and diabetic patients with normal renal function, but not in patients with chronic renal failure. The value of 1,5-AG varies wider than that of HbA1c. CONCLUSIONS: 1,5-AG showed close correlation with glucose and HbA1c and detected subtle changes in glycemia. Therefore, measurement of 1,5-AG would be useful in monitoring glycemic control in diabetic patients with normal renal fucntion. But it would be inappropriate to use 1,5-AG for the evaluation of glycemic control in patients with renal failure.