BACKGROUND: Routine renal function tests are not sensitive enough to detect early renal complication of diabetes. To detect the complication as soon as possible, we measured urine N-Acetyl-beta-D-glucosaminidase(NAG) and evaluated in comparison with microalbumin and beta2-microglobulin(beta2-MG). METHODS: 87 patients with type II diabetes visited Catholic University Hospital of Taegu Hyosung during the period October 1995 to March 1996. We collected 24 hour urine samples and measured NAG, albumin excretion rate (AER), beta2-MG. urinalysis, BUN, creatinine(Cr) Cr clearance(CrCl), fasting and 2 hour postprandial blood sugar and hemoglobin A1c. RESULTS: The average age of the patients was 53+/-15 years old and their average disease duration was 5.8+/-5.0 years. Abnormal rates of each renal function tests were as follows : NAG/gCr 52.1%, AER 51.7%, CrCl 42.5%, BUN 18.4%, beta2-MG 13.8% and creatinine 6.9% in order. From 36 patients whose AER was within normal limit, 13 of them(36.1%) showed increased level of NAG/gCr. Of 38 patients with increased NAG/gCr results, the 31 patients (81.6%) recorded abnormal results of renal function tests. Among 87 patients studied 60 patients(68.5%) showed increased level of NAG/gCr or AER results. Compared with AER test alone. the combined tests with NAG/gCr increased 16.8% of detection rates of renal complication in type II diabetes. CONCLUSION: Urine NAG/gCr and AER tests were very useful for detecting the early renal complication of type n diabetes. As increase of NAG/gCr suggest the proximal tubule damage, it is necessary to have further evaluation about the proximal tubule damage of renal complication in type II diabetes.