Gene therapy represents a potential new strategy for cancer treatment. In order to deliver a transgene into target tumor cells, a vector system is required. To date, most of the cancer therapies are based on the use of different viral vectors. However, bacteria such as Salmonella, Clostridium or non-pathogenic Bifidobacterium can selectively accumulate in tumors in vivo what renders them useful for cancer gene therapy vectors. Although the mechanism of DNA transfer from bacteria to mammalian cells is not completely understood their potential to deliver therapeutic genes into tumor cells have been demonstrated in vitro and in vivo. The review presents recent achievements in bacteria-mediated cancer gene therapy.