We describe a novel strategy for expression of GFP in mammalian mitochondria. METHODS: The key components of the strategy were an artificially created mitochondrial genome pmtGFP and a DQAsome transfection system. RESULTS: Using immunofluorescence and a combination of immunohistochemical and molecular based techniques, we show that DQAsomes are capable of delivering the pmtGFP construct to the mitochondrial compartment of the mouse macrophage cell line RAW264.7, albeit at low efficiency (1-5 ), resulting in the expression of GFP mRNA and protein. Similar transfection efficiencies were also demonstrated in a range of other mammalian cell lines. CONCLUSIONS: The DQAsome-transfection technique was able to deliver the exogenous DNA into the cellular mitochondria and the pmtGFP was functional. Further optimization of this strategy would provide a flexible and rapid way to generate mutant cells and useful animal models of mitochondrial disease.