The authors present materials for comparison of three methods of E. coli infection by the RNA of the MS2 bacteriophage. The cells accepted the RNA at the stage of spheroplasts (obtained with the aid of a lysozyme and EDTA) with the efficacy of up to 1.5 X 10(5) IC/mug of the RNA. Diethylpyrocarbonate was used as a transfection stimulant. The product of transfection was identical to the MS2 bacteriophage. The efficacy of transfection in the calcinated system and on the frozen-defrosted bacteria was lower than on the spheroplasts (10(2) IC/mug of the RNA) which was largely associated with the formation of "latent infectious centres". Formation of latent negative colonies was characteristic of bacteriophage MS2, but formation of these colonies was intensified when calcinated cells were used for transfection.