Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined in 8 patients with disseminated testicular carcinoma before, during and 1 year after termination of a combination chemotherapy with cis-diamminedichloroplatinum (CDDP). The decrease in median GFR in comparison with the pretreatment value was 15.5% at the start of the maintenance therapy, 23% at the end of the maintenance therapy and 15.5% 1 year after termination of therapy. The comparable reduction in ERPF at those instants was 15.5, 19 and 23.5%, respectively. At all intervals the changes in GFR were significantly reduced in comparison with pretreatment values. No significant change in both GFR and ERPF was found either during or after discontinuation of maintenance treatment. The fall in ERPF was significant during the total period of treatment as well as during the total time of observation. Thus, no cumulative nephrotoxicity during therapy, nor improvement in renal function thereafter was found. Serum levels of creatinine and beta-2-microglobulin did not express the changes in renal function.