Comparative electron microscopic analysis of the patterns of centriolar and cytoplasmic microtubules immunostaining for acetylated or tyrosinated alpha-tubulin was performed during the cell cycles of the mouse diploid 3T3 (A31) and virus-transformed heteroploid SV40-3T3 cell lines. It was shown that the pattern of centriole immunostaining changed during mitosis in control 3T3 (A31) cells, but not in tumorigenic SV40-3T3 cells. A sharp change in the pattern of centriole immunostaining was observed in those cell cycle periods when the protein organization of centrosome underwent changes during interphase/mitosis or mitosis/interphase transitions due to the rearrangement of microtubule system. A high level of centriole immunostaining for tyrosinated and acetylated alpha-tubulin was observed at all cell cycle stages with the exception of entering mitosis for the former and the end of mitosis for the latter.