Objective: Purpose to investigate the different in vitro function of targetable non-viral vector containing poly-L-lysine or protamine. Methods: Using GV1 and GV2 targetable non-viral vectors, the influences of the poly-L-lysine and protamine on in vitro gene transfer efficiency and the course of gene expression were observed. Results: ?-galactosidase was expressed at intermediate level (50% ) in A375 cells using a complex containing either protamine or poly-L-lysine. Howerver, in case of ABAE cells, ?－galactosidase expression level was low (20% ) transferred with a comPlex containing protamine. On the contrary, ?－ galactosidase expression was at high level (70% ) provided that protamine was replaced with poly-L-lysine. In addition, ?-galac- tosidase activity reached the peak at the 6th day after transfection with the complex containing protamine. The expression was not altered with subsequent subcultures, at least for 3 passages. Using poly-L-lysine, the expression peak in A375 reached the peak at the 7th day after transfection, but the level declined along with subsequent passages of cells. Conclusion: The apllication of protamine in VEGF receptor mediated gene delivery system was limited.