Experimental studies indicate that administration of angiogenic proteins or genes by the epicardial or intracoronary route can stimulate development of new collateral vessels and improve myocardial perfusion. An endocardial catheter‐based approach to this therapy would obviate the need for surgery, while preserving the effectiveness of direct intramyocardial administration. Fluoroscopic guidance and prototype, preformed, coaxial catheters were used to examine the feasibility of percutaneous catheter‐based adenovirus (Ad)‐mediated gene transfer and expression in normal swine myocardium. The feasibility of intramyocardial administration (100 μl/injection) of a radiocontrast agent and black tissue dye to all regions of the left ventricle (septum, anterior, lateral, and inferior wall) was confirmed fluoroscopically and on postmortem examination. Injections of replication‐deficient adenovirus (10 injections of 10¹¹ particle units/100 μl each) coding for β‐galactosidase (Adβgal) or vascular endothelial growth factor (Ad_GVVEGF121.10) were administered to the left ventricular free wall to examine endocardial based gene transfer and expression. β‐Galactosidase activity was detected by histochemical staining and quantitative assay in targeted regions of the myocardium. Regional VEGF expression was found to be significantly greater in targeted regions (1.3 ± 0.4 ng/mg protein) as compared with non‐targeted regions (0.3 ± 0.1 ng/mg protein) or regions injected with control (Adβgal) virus (0.2 ± 0.03 ng/mg protein, P < 0.001). Catheter‐based Ad mediated endocardial gene transfer and expression is feasible using percutaneous, fluoroscopically guided, preformed, coaxial catheters. This approach should be clinically useful to administer angiogenic genes to the ischemic myocardium. Cathet Cardiovasc Intervent 2001;52:260–266. © 2001 Wiley‐Liss, Inc.