[en] Investigation of labelling index and growth fraction in vitro, cell survival and cell population kinetics in diffusion chambers and changes in the cell kinetic parameters after irradiation were performed on surgery material and biopsies from human tumors of various types. The analysis of results obtained using the diffusion chambers and in vitro system demonstrate variability in labelling index within tumors of various type, individual differences and variation within the same tumor. Significant variability of growth fraction in individual tumors was also noted, however, in many instances, most of the cells in the tumor were not proliferating. The growth fraction in gliomas and tumors of the floor of the mouth was greater in tumors with a high labelling index, in patients with a short tumor history and in patients with a short nonrelapse period. In the same groups of tumors changes of labelling index growth fraction during radiotherapy were compared with the therapeutic response of tumors. It can be concluded that the initial parameters of proliferative activity (labelling index and growth fraction) did not determine the radiation response of tumors but the dynamics and the intensity of their changes during the treatment were more informative in this respect. Complete regression of tumor may be expected only with decrease of labelling index and growth fraction. (author)