The activity of granulocytic myeloperoxidase (MPO) was investigated in 45 patients with renal cancer before and 14 days after renal artery embolization in comparison with control group of 40 healthy people. The group examined showed lower MPO activity before embolization, as compared to controls. The differences being statistical insignificant (p > 0.05). After embolization the activity MPO was normalized, reaching the mean value of control group. The findings revealed reduced granulocytic MPO activity in patients with renal cancer.