A temperate phage Ml, infective towards some R. meliloti strains, was isolated from soil taken from local fields. Its morphology, host range, transducing ability and the locations of restriction endonuclease cleavage sites on the genomes were determined. Phage Ml was classified as belonging to B BRADLEY's group bacteriophages because of the hexagonal outlines of its head and its long, flexible and non-contractible tail. The molecular weight of phage DNA was estimated to be 54.1 ± 1 kilobases (kb) and it corresponded to the value expected for capsid size – 70 nm. Phage Ml carries out general transduction and forms stable lysogens with the R. meliloti strain L5.30.