The aim of the study was an evaluation of circulatory system functions in patients with Wilms' tumour who underwent the multidrug chemotherapy with anthracyclines. The investigation was carried out on 43 patients after chemotherapy between 1994-1997, from 4 centres of paediatric oncology (in Gdansk, Poznan, Lublin and Bydgoszcz). All patients were divided into two groups. The children from the first group received anthracyclines without Cardioxan protection. The patients from the second group had been treated with both anthracyclines and Cardioxan. The cardiotoxicity was estimated in relation to the total dose of anthracyclines. Comparing the side effects of chemotherapy in both groups there were no essential differences in bone marrow suppression and in hepatotoxic symptoms.