Mechanism of aminoglycoside nephrotoxicity is yet unclear. Reduction of 20 p. cent of glomerular filtration initial value is observed in 10 p. cent of cases. Aminoglycoside nephrotoxicity appears to be related to high doses, to duration of treatment and also to individual factors such as age and preexisting renal impairment. No mean of predicting aminoglycoside nephrotoxicity without any error is available. Meanwhile, accurate measurement of glomerular filtration and of beta 2-microglobulin urinary elimination seems clinically more usefull for detection of impaired renal function than uneasy measurement of urinary enzyme excretion and than monitoring the aminoglycosides serum concentrations.