The variables involved in the transfection of epithelioma papulosum cyprini (EPC) cells (a representative carp fish cell line) with the genes for beta -galactosidase from E. coli, for luciferases from firefly or renilla, for the G protein of viral haemorrhagic septicemia virus or for green fluorescent protein under the cytomegalovirus, the SV40 or the T7 polymerase promoters have been studied. Fugene was selected among 10 transfection different reagents because it is simpler to use and it induced maximum efficiences of transfection of 37% equivalent to 10-15 ng beta -galactosidase per 500 000 EPC cells.