The integration of the λ phage genome in the absence of site specific recombination was investigated. An int through red gene deleted λgal bio transducing phage was infected onto gal through uvrB gene deleted E. coli cells of rec⁺ or recA. Rare lysogens were selected as the gal⁺ transductants on minimal agar which contains galactose as a sole carbon source. All of the gal⁺immλ⁺ transductants examined carried prophage genomes within the host chromosomes. The integration of λgal bio phage genome into the rec⁺ host seemed to occur about 300 times more efficiently than in the recA strain. Approximate chromosomal locations of these prophage genomes were mapped by mating experiments. Eight independently isolated gal⁺rec⁺ lysogens were all found to have the prophage genomes near the nalA gene. Among nine independently isolated gal⁺recA lysogens, eight lysogens had the prophage genomes near the lac gene and the remaining one near the rac gene. The prophage gene order was examined in the three rec⁺ and four recA lysogens by deletion mapping and all of the λgal bio genomes present within these lysogens were found to have been integrated by the crossover occurring somewhere between J and gal of the transducing phage genome. General properties of these lysogens were examined.