As a matter of fact, most of the information about transfection efficiency of different Drosophila cell lines rests upon personal communications, among our small community of drosophilists, and only two published reports dealt especially with this important problem. Mammalian cell cultures can be synchronized with various methods, and several investigators could thus study the influence of the cell cycle on the efficiency of transfection. Huge differences in the expression of any given gene should naturally be expected after its transfection into different cultured cell lines, even though the tissue origin of most available Drosophila cell lines remains unknown. Transfection efficiency, as estimated from frequencies of transformation and/or expression levels of transferred genes, may vary considerably, in function of the used Drosophila cell line, and even sometimes from one subline to another. For transferring genes, it is essential to have at one's disposal proficient recipient cells.