Two types of cell cultures, BSC and HE-p2, have been studied from the microelectrophoretic point of view. Determinations have been made for infected cells (collected at 48 or 72 hours after infection) and for control cells, immediately after their separation from the culture, or after preserving them for 24 hours or more in migration buffer. The electrophoretical mobility increases with an average of 10% in the case of infected cells, as compared to the controls. This parameter offers a distribution of values varying from the gaussian curve to the bimodal one. From the microelectrophoretic point of view, the HEp-2 cells are more stable and respond more uniformly than BSC cells.