Bacterial conjugation, in which DNA is transferred from one bacterium to another, was first reported in 1946 and found to be mediated by the F factor. Although the F and RK2/RP4 prototypic plasmids can mediate the transfer of DNA from bacteria to yeast, there has been no evidence of classical bacterial conjugation to higher eukaryotes. Here, I present evidence of such transfer, using Escherichia coli, the RK2 plasmid system and Chinese hamster ovary CHO K1 cells.