To clarify the relationship between early diabetic nephropathy and the glycemic control in non-insulin-dependent diabetes mellitus (NIDDM) without hypertension, excretion of urinary albumin was studied retrospectively for 8 years. The patients with early diabetic nephropathy were divided into two groups according to the initial urinary albumin index (UAI: mg/g.creatinine), namely, a normoalbuminuric (less than 15 mg/g.creatinine) and a microalbuminuric group (15 < or = UAI < 200 mg/g.creatinine). Comparisons of changes in UAI were made between good (HbA1 < 9.0% and fasting plasma glucose (FPG) < 140 mg/100 mL throughout the observation period) and poor glycemic control groups after 4 and 8 years. In the patients with normoalbuminuria at the initial determination, five of 11 patients (45.5%) with good glycemic control and 14 of 22 patients (63.6%) with poor glycemic control became microalbuminuric after 8 years, respectively (p < 0.05). In the microalbuminuric patients, five of ten patients (50%) with poor glycemic control became macroalbuminuric (UAI > or = 200 mg/g.creatinine), although only one case worsened of five patients with good glycemic control (p < 0.05). In conclusion, the development or progression of early diabetic nephropathy in NIDDM was significantly inhibited by good glycemic control (FPG < 140 mg/100 mL and HbA1 < 9.0%), independent of hypertension, and probably irrespective of the mode of therapeutic intervention.