Аннотация:Comparative study has shown that by the gel diffusion assay both anti-HEp-2 virus serum and anti-breast cancer milk ultrasediment serum precipitated an identical antigen in human milk specimens, which was not identical with the group specific antigen of the HEp-2 virus. At the same time tha anti-breast cancer milk serum did not precipitate the HEp-2 virus. However, molecular hybridization experiments revealed nucleotide sequences homologous to nucleic acids of oncornavirus of D-type in milk obtained from breast carcinoma patients as well as in milk of healthy donors.