The prognosis of many paediatric malignancies has been improved since escalation of dose intensity. There is a higher acute toxicity due to chemotherapeutic treatment. The present study was performed to evaluate most common side - effects related to different doses of iphosphamide in various cytostatic regimens. Authors evaluate 177 courses in 34 patients: 54 courses according to protocol POG 9354 for Ewing sarcoma - iphosphamide (6 or 9 g/mz) combined with etoposide (500 mg/mz), 45 courses of regimen IVA (iphosphamide 6 or 9 g/mz, vincristine 1.5 mg/mz, actinomyzcin D 1.5 mg/mz) and 23 courses of regimen IVE (iphosphamide 9 g/mz, etoposide 450 mg/mz, vincristine 1.5 mg/m ) according to protocol MMT 953A and 953B for malignant mesenchymal tumours, 55 courses of regimen ICE (iphosphamide 9 g/mz, carboplatinum 800 mg/mz, etoposide 500 mg/mz) administered to patients with refractory or recurrent solid tumours. Authors evaluated acute haematological and nonhaematological toxicity according to WHO classification. They also recorded number of hospitalizations due to febrile neutropenia and delays between courses. Conclusion: The highest toxicit was induced by Chemotherapy ICE and courses of iphosphamide (12 g/mz) combined with etoposide 500 mg/m . The haematological toxicity grade IV was in both regimens (100% and 91 % respectively) number of hospitalizations due to febrile neutropenia (51 % and 29 % respectively). There was grade HI neurotoxicity during three courses and gastrointestinal toxicity grade HI during five courses of both these chemotherapeutic regimens. Reduction of cytostatky due to toxicity was necessary on eight courses. There was evidence of microscop~ic haematuria in eight courses of ICE regimens. Only one patient treated with the IVA regimen (IFO 6 g/m ) developed repeatedly macroscopic haematuria. The chemotherapeutic schedule with iphosphamide (6 or 9 g/mz) combined with vincristine, actinomycin D or etoposide esere tolerated well - predominantly acute haematological toxicity gr. II - HI and nonhaematological toxicity gr. I - II. With appropriate supportive care all these chemotherapeutic regimens have an acceptable toxicity.

        Key words: iphosphamide, children, acute toxicity, combination of cytostatics