OBJECTIVE To evaluate the abilities of recombinant adenovirus carrying the basic fibroblast growth factor (bFGF) gene to (1) produce bFGF protein in vitro and (2) rescue retinal photoreceptors in Royal College of Surgeons (RCS) rats in vivo. METHODS Cultured human retinal pigment epithelial cells were infected with one of the following two replication-deficient adenoviral vectors that drive inserted genes by beta-actin promoter with cytomegalovirus enhancer: AxCAJSbFGF, which expresses the human bFGF gene, and AxCAlacZ, carrying the cDNA of bacterial beta-galactosidase as a viral control. These viruses and recombinant bFGF protein were also injected into the subretinal space of RCS rats at the age of 21 days. The production of bFGF was evaluated by an immunohistochemical method in vitro and in vivo. The secretion of bFGF produced in vitro was quantified by an enzyme-linked immunosorbent assay. The thickness of the outer nuclear layer (ONL) as a marker of photoreceptor cell rescue was estimated at 2, 28, and 56 days after the injections. RESULTS AxCAJSbFGF produced human bFGF protein effectively both in vitro and in vivo. The semiquantitative analysis of ONL thickness revealed a significant protective effect of AxCAJSbFGF and the recombinant bFGF protein injection up to 56 days after injection. CONCLUSIONS These results demonstrate that a recombinant adenoviral vector can achieve the transfer of bFGF gene in vitro and have a protective effect for photoreceptor cells in vivo. Gene therapy with a bFGF-expressing recombinant adenoviral vector may provide a new strategy with which to target retinal degenerative diseases.