Conjugative-like transfer of hybrid plasmid RP4::Mucts62 from Escherichia coli to plasmid-free Bacillus polymyxa was carried out. Bacillus transcipients are detected by the markers of kanamycin and tetracyclin resistance RP4 and thermal sensitivity to growth at 40-42 degrees C, determined by prophage Mucts62 in the plasmid. The technique of transception using millipore filters on solid media has been improved. For comparison with experimental samples, restriction mapping of the native plasmid in donor E. coli GA570 strain was carried out with identification of the prophage location in point 30.5 n. p. of RP4 map with counter-clockwise orientation of the right terminal towards IS21 element. Two phenotypes of bacillus transcipients selected for restriction mapping were singled out. Phenotype KmRTcRTS retains all markers of donor strain plasmid, and by the sum of restricts electrophoretically either corresponds to intact hybrid plasmid or contains deletions in RP4 sites (1-8 n. p.) adjacent to the left arm of prophage or rarely on the right arm (up to 3 n. p.). KmRTcRTS transcipients lose kanamycin resistance and on restriction map show greater prolongation of deletions from the prophage right terminal to kan RP4 gene, shortening it to 13 n. p. without involving the prophage proper. Its left terminal is retained, but 2-7 n. p. sites are deleted in the RP4 area adjacent to it. The possibility of transception in nature and horizontal routes of drug resistance dissemination among genetically remote bacteria are discussed.