Serum creatinine levels were determined prospectively every 2 to 3 months in 40 patients with diabetic nephropathy for a global observation period of 864 months. The monthly creatinine increasing rate was significantly lower in normotensive periods, mean arterial pressure (MAP) less than 115 mmHg, when compared with hypertensive periods, MAP greater than 125 mmHg. No significant difference was shown in periods with borderline hypertension (MAP between 115-124 mmHg). The mean creatinine increases were of 0.036 mg/dl/month, 0.3 mg/dl/month and 0.046 mg/dl/month respectively. Normotension was associated with a slowing down of the rate of decline in renal function in this group of moderate kidney failure with an initial mean serum creatinine of 2.26 mg/dl. The exposure of patients to nephrotoxics (aminoglycosides, and possibly anesthesia) significantly accelerated the decline in renal function: 0.39 mg/dl/month and 0.17 mg/dl/month respectively according to the concomitance or not of toxics and hypertension. The reported protective effect of diabetes against aminoglycosides nephrotoxicity in experimental conditions was not reflected in our clinical results. On the contrary, we suggest a possible enhanced sensibility of the diabetic patient with diabetic nephropathy to aminoglycosides leading to an acceleration of the progression of renal failure.