Enzymuria is a well known parameter of evaluation of drugs nephrotoxicity, particularly of antibiotics. Alanine aminopeptidase (AAP), gamma-glutamyltransferase (GGT) and N-acetyl-bêta-D-glucosaminidase activities were measured in native urine. This study included 19 patients treated by an association of netilmicin-vancomycin. Enzymuria was measured on 24 hours urines at J0 then every two days during treatment. Enzymuria increased 24 or 48 hours after the beginning of the treatment. The Principal Components Analysis (PCA) of the results of enzymuria, seric urea and creatininemia shows the presence of two groups of responses. The first principal component exhibits two populations: the patients with pathological seric urea and pathological seric creatinine and the others. The PCA does not allow this discrimination using only the results of enzymuria; in contrast, with these results, the patients may be classified by the PCA on the basis of treatment duration. The enzymuria allows the clear identification of nephrotoxic drugs but does not allow the prediction of renal injury or of its aggravation.