We examined liposome-mediated gene transfection of nerve growth factor (NGF) in primary central nervous system cultures. RT-PCR analyses detected increased expression of NGF mRNA one day after liposome-mediated NGF gene transfection. ELISA studies detected large increases in NGF protein in cells and in culture medium after NGF gene transfection. Cells continued to secrete NGF into the medium for at least 2 weeks. NGF bioassays confirmed that the NGF secreted after gene transfection was biologically active.