The dynamics of Blastocystis hominis reproduction in vitro in Pavlova's and Nelson-Jones media was studied. The time of generation in these media was 21.5 and 16.7 h, respectively. The duration of the lag phase was 1 day, of log phase 2 days, and of the stationary phase 6 days in both cases. The cell count in the logarithmic phase increased at the expense of the vacuolar forms proliferation. During the stationary phase, the granular forms quantitatively predominated over vacuolar forms, the share of the granular forms reaching almost 100% at late stages of the subculture development.