The sensitive parameters of tubular nephrotoxicity during 4-day chemotherapy with new combination schedule of cisplatinum and 5-fluorouracil were followed. The determinations of tubular enzymes beta-glucuronidase (GRS) and gamma-glutamyltransferase (GMT) in 24 hours urine, the excretion of creatinine and proteinuria were assayed before therapy and during 4 consecutive days of treatment. We recorded the significant increase of protein excretion and only slight increase of GMT and GRS activities after chemotherapy. The decrease of the creatinine excretion on the 3rd day of therapy was not statistically significant. Simultaneously followed serum creatinine and urea levels proved the elevation of creatinine only in 1 patient (the 1st grade according WHO classification). Our results suggest that the performed regime of chemotherapy produces only very low nephrotoxicity comparing to the 1-day administration of cisplatinum. These conclusions are confirmed also by the former examinations of GRS activities in cisplatinum therapy.