The neural retina is a logical target of gene therapy for highest degree of gene expression was obtained by various ocular diseases. We developed a new gene delivmethods A (23.2% of total retinal area) and C (19.8%), ery method to the neural retina using an adenoviral vector while the lowest degree was obtained by method B (8.9%). with a high degree of gene transfection efficiency and lessThe inflammation was observed in all eyes and the value functional damage. An adenoviral vector bearing the lacZ of inflammation was quantified as the average inflammagene (AdCALacZ) was injected into the eyes of adult Wistory cell number in each microscopic field (cells per fields). tar rats after an SF 6 compression gas vitrectomy and left A moderate degree of inflammation was induced by for 30 min followed by washing with balanced salt solution methods B (28.3 cells per field) and C (27.5 cells per field) (BSS) (method A). Three other methods, comprising a simand a minimal degree of inflammation was induced by ple intravitreal injection (method B), an intravitreal injection method A (11.2 cells per field). We evaluated the retinal after an SF6 compression gas vitrectomy (method C) or a function by measuring an electroretinogram (ERG). The subretinal injection (method D), were also studied. The amplitudes of the ERG were depressed in all eyes treated gene expression was examined 6 days after the AdCAwith AdCALacZ. This depression was manifested most by LacZ injection. An immunohistochemical study for antimethods B and C, and least by method A. The deteriovimentin, antiglial fibrillary acidic protein and anti S100 ration in the ERG findings seemed to correlate with the protein antibodies showed the neural retinal cells (Mü ller intensity of inflammation. Our study showed that an intravicells) to be primarily transfected by methods A, B and C, treal injection with an adenoviral vector can transfer the while only a few cells were transfected by method D. The genes to the neural retinal cells and therefore a vitrectomy expression of -galactosidase was visualized by X-gal and the subsequent removal of the adenoviral vector, can staining and the positive areas on each hemiflat mount thus significantly improve the transfection efficiency and specimen were measured by an image analyzer and then also reduce the degree of functional damage. were adopted as a value of gene transfer efficiency. The