Hypothesis: To investigate the feasibility of gene therapy of the middle ear mucosa using a novel vector. Background: Given present medications are unable to affect chronic otitis media, cholesteatoma, or tympanic membrane perforation, newer methods of treatment like gene therapy for these diseases must be explored. These genes can then be used to alter cytokines in the middle ear, slow or stop cholesteatoma growth, or improve tympanic membrane perforation healing. Feline immunodeficiency virus (FIV), a new lentiviral vector has been found to have greater than 90% efficiency in transfecting epithelial cells. Therefore, in vivo gene therapy of middle ear mucosa cells was attempted. Methods: Twenty microliter of 5 x 10(5) vectors per ml FIV carrying the gene for green fluorescence protein (GFP) was introduced into the middle ears of Sprague-Dawley rats via a bulla approach. Results: Expression of the GFP gene was observed in the middle ear mucosa cells at 1 week post-inoculation indicating transfection. Conclusion: Gene therapy of the middle ear is feasible with a FIV-based vector. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.