To determine the usefulness of recombinant Sendai virus (SeV) for ocular gene transfer, the authors characterized SeV-mediated gene transfer to the retinal tissue of adult rats via subretinal injection. Recombinant SeV encoding the lacZ gene achieved frequent transgene expression in the retinal pigment epithelium (RPE) (mean=38.76%), while gene transfer to other retinal cells was rare. These findings are similar to those of previous reports using adenoviruses. Peak reporter gene expression of SeV in cultured RPE cells was similar to that of adenovirus at the same titer; however, SeV achieved high levels of expression after a brief vector-cell contact time, while adenovirus required over 3hr for efficient gene transfer. This finding was also observed in vivo following a brief SeV filling in the subretinal space, and may therefore provide a clinical advantage in avoiding retinal damage due to prolonged detachment. The observed SeV-mediated gene expression in the rat retina was transient. The initial phase of the decrease in luciferase activity could be prevented by daily eye drops of dexamethasone, suggesting that the corticosteroid-sensitive host reaction may affect early clearance of the virus. The late decline of transgene expression (2 weeks) was inhibited by the immunosuppressant, cyclosporin A, in a dose-dependent manner, suggesting that the cytotoxic T-lymphocyte response may be important in this phase. This work represents the first report of SeV-mediated gene transfer to ocular tissue, and identifies recombinant SeV as a new tool for studies of retinal gene transfer and gene therapy.