Integration of T-DNA into the maize genome as a result of treatment of silks with Agrobacterium cells, containing activated vir genes, was demonstrated. In planta treatment of maize (Zea mays L.) was performed during flowering in field. Cell suspension of Agrobacterium tumefaciens line GV3101(pTd33), carrying activated vir genes, was applied onto the previously isolated silks, which were afterwards pollinated with the pollen of the same cultivar. Integration of T-DNA into maize genome was confirmed by PCR (the nptII and gus reporter genes) and hystochemical staining of the seedling tissues, obtained from the transformed seeds. Amplification of the nptII gene showed the presence of about 60.3% of PCR-positive plants out of the total number of kanamycin-resistant seedlings examined, or 6.8% of the total of number of seedlings.