Recombinant f1 phages carrying a shuttle vector pKA1M for expression of blasticidin S deaminase were introduced into monkey COS7 cells by mixing with dioctadecylamidoglycylspermine (DOGS). Blasticidin S selection resulted in the detectable growth of resistant colonies within a week. The transfection efficiency depended on the amounts of the phage and DOGS, their ratio, and the time during which the cells were incubated with the phage/DOGS mixture. This method requires only several microliters of an Escherichia coli culture medium containing recombinant f1 phage particles and is applicable to various cell lines including mouse NIH/3T3, chinese hamster CHO-K1, and human HT-1080.