Type 2 diabetes mellitus is the main cause of increase in patients suffering from end-stage renal failure in France. We performed an observational study of the change in renal function of type 2 diabetic patients, attending our diabetology clinic. Clinical and biological data were regularly entered in an informatic database (Pénélope, Poitiers University Hospital). We prospectively followed 351 type 2 diabetic patients (age at diagnosis: 40 to 75 years), for 32 months (extremes: 1-120). Renal function was graded in 4 stages according to plasma creatinine and urinary albumin excretion (UAE) determined by nephelometry on random urinary sample: absent (UAE < 20 mg/L et creatinine < 150 mumol/L), incipiens (UAE 20 to 200 mg/L and creatinine < 150 mumol/L), established (UAE = 200 mg/L et creatinine < 150 mumol/L) advanced (creatinine = 150 mumol/L). Glycated haemoglobin (HbA1c) was determined by HPLC. Systolic/Diastolic Blood Pressure (SBP/DBP) was measured with a mercury sphygmomanometer. We defined renal events as the change from one stage of nephropathy to a higher one. A total of 351 type 2 diabetic subjects were studied: 194 men/157 women mean age 63 +/- 11 years, mean diabetes duration 10 +/- 9 yr. At baseline, 206 patients had no nephropathy, 98 incipient nephropathy, 28 established nephropathy and 19-advanced nephropathy. Baseline stage of nephropathy was related to SBP (p < 0.0001), DBP (p = 0.0002), diabetes duration (p = 0.0064) but not HbA1c (p = 0.2182) or sex (p = 0.4794). Among those 332 subjects without baseline advanced nephropathy, 134 progressed in nephropathy. Progression of nephropathy was not related to the presence of hypertension (SBP/DBP > or = 160/95 mmHg) (log-rank = 0.22; p = 0.6377). Conversely, patients with a poor glycaemic control (HbA1c > or = 10%) had a worse renal-event free survival (log-rank = 4.89; p = 0.0269). Glycaemic control is a risk factor for the progression in nephropathy of type 2 diabetic patients.