Creatinine clearance and beta-D-acetyl-glucosaminidase (NAG) were useful markers for the evaluation of the renal function of 57 cases of head and neck cancer treated with 60 mg/m2 cis-platinum (CDDP). There was a significant correlation between creatinine clearance and NAG values for (r = -0.4820, p less than 0.01). The nadir of creatinine clearance and NAG values were observed between 2 and 3 weeks after administration of CDDP. After 2 courses of chemotherapy with CDDP, more nephrotoxicity was observed in the cases received prior CDDP therapy, than cases without chemotherapy statistically. Combined chemotherapy with CDDP and 5-FU (CF therapy) caused more renal damage, comparing with other combined chemotherapy such as COP therapy (CDDP, vincristine and peplomycin), and CAP therapy (CDDP, aclacinomycin and cyclophosphamide). Early recovery from the renal damage following CDDP therapy was detected in the cases given Fosfomycin (FOM). This results suggest that FOM would be effective for decreasing the nephrotoxicity by CDDP.