Cationic lipid-DNA complexes are being evaluated for local or systemic therapeutic gene transfer. These positively charged liposomes fuse with negatively charged cell membranes and deliver the enclosed plasmid and its encoded gene to target tissues. This system has relevance for delivering genes to both normal and damaged or malignant tissues including phagocytes, tumor cells, endothelium and possibly parenchymal cells. Among the approaches being actively evaluated is the delivery of immunostimulatory cytokine genes (such as IL-2, IFN alpha or IL-12) into tumors. It is hypothesized that the local cytokine release will attract or induce antitumor immune responses. Valentis, (formerly GeneMedicine), has developed a plasmid encoding human IL-2 complexed with the liposomal preparation of DOTMA and cholesterol and has initiated phase I studies of intratumoral injection in head and neck cancer patients. Other routes of administration (intravenous and intratracheal), cytokines (IL-2) and proprietary liposomal-DNA complexes are being evaluated in preclinical models.