A β-galactosidase gene expression construct was used to investigate the effectiveness of gene delivery and expression when DNA/liposome complexes were topically applied to mouse skin in vivo. DNA was complexed with a commercial preparation of N-[1-(2,3-dioleoyloxy) propyl]-N, N, N-trimethyl-ammonium-methyl-sulphate (DOTAP) in a ratio of 1:1.6 (w/w). The DNA rapidly penetrated the skin and was expressed in the epidermis, dermis and hair follicles. A DNA concentration of 267 μg/ml DNA was found to be optimal for efficient transfection. Expression was seen as early as 6 h post-application, persisted at high levels 24 and 48 h post-treatment, but was markedly reduced by 7 days after application. In conclusion, utilising a commercially available liposome preparation, topically-applied DNA/liposome complexes can be efficiently delivered and expressed in several cell types within the skin. This simple, non-invasive technique may have implications for a number of gene therapy applications.