A method of transferring a gene to vertebrate cells is disclosed. The method comprises the steps of: (a) providing microprojectiles, the microprojectiles carrying polynucleic acid sequences, the sequences comprising, in the 5' to 3' direction, a regulatory sequence operable in the tissue cells and a gene positioned downstream of the regulatory sequence and under the transcriptional control thereof; and (b) accelerating the microprojectiles at the cells, with the microprojectiles contacting the cells at a speed sufficient to penetrate the cells and deposit the polynucleic acid sequences therein. Preferably, the target cells reside in situ in the animal subject when they are transformed. Preferred target cells are dermis or hypodermis cells, and preferred genes for insertion into the target cells are genes which code for proteins or peptides which produce a physiological response in the animal subject.