Cardiac function was monitored by means of impedance cardiography in the early phase of chemotherapy in 30 patients with hematological malignancies. The patients were divided into two groups according to whether or not they revealed cardiac risk factors (age > 65, coronary heart disease, cardiac failure, hypertension, diabetes mellitus or prior mediastinal irradiation). It was found that the mean values of cardiac and stroke indices before chemotherapy were significantly lower in patients with cardiac risk factors. It was also noted that the mean values of these indices in both groups did not change significantly after anticancer treatment. However, in two patients a significant decrease of cardiac indices was observed. On the other hand, in several patients an increase of cardiac and stroke indices was recorded. It seems that careful measurements of cardiac function in cancer patients by impedance cardiography enable to analyze the influence of anticancer drugs upon the cardiovascular system. The results of these measurements may be used for the individualization of cancer therapy.