It has been shown that the culture of Bacillus thuringiensis subsp. gall. 69-6 dissociates into R- and S-variants in chemostat. Although under some conditions the sporogenesis and the synthesis of S-variant toxin began two hours earlier than these processes in R-variant cells which were observed, respectively, after 10 or 12 hours from the beginning of the experiment, the intensities of sporogenesis and toxin production as well as the exit of spores and toxin excretion from cells were similar after 24 hours. The resistance to the bacteriophage present in chemostat was the advantage of S-variant cells. The data obtained by electron microscopy indicate that the phagoresistance is caused by the structural organization of the S-variant cell wall. Its peptidoglycan component is thin and is distinguished by crumb structure. By means of negative contrast microscopy it was found that the surface T-layer of R-variant cell wall was characterized by the tetragonal packaging of protein subunits indicating the regular orientation of phagoreceptors in it. The redistribution of protein subunits in the T-layer of S-variant cell wall prevented from the adsorbance of bacteriophages on the cell surface. The adsorbance of phages on the surface of R-variant cells was observed rather often. It led to the degradation of peptidoglycan, the formation of protoplasts and lysis.