Electroporation represents a powerful technique for cell transfection; however, its efficiency in haemopoietic cells (approximately 1%) is largely unsatisfactory. Biological processes in haemopoietic cells are often studied using leukaemia cell line HL-60. For this reason we developed conditions for efficiently introducing plasmids to HL-60 cells by electroporation, as an alternative to other techniques. This technique employs the electric pulse (250-270 V; 1000 microF) followed by separation of living cells on a Ficoll-Paque discontinuous gradient. Using 10-20 micrograms of plasmid, we routinely achieve 12-14% of transfectants.