One approach to gene therapy for human cancer is transcatheter injection of DNA liposomes into tumor masses. To determine the feasibility of selective delivery of recombinant genes by a catheter to the pulmonary vasculature in humans, a patient with melanoma received two treatments of HLA-B7 plasmid DNA complexed to cationic liposomes into a right posterior basal pulmonary artery associated with a mass lesion. The treatments were well tolerated. No adverse respiratory, cardiac, immunologic, or other organ toxicities were detected. The delivery of recombinant genes by catheter may be a useful modality to treat human malignancy and other diseases.