We have been conducting ophthalmic examinations in rats and accumulating back ground data during the past 6 years. Approximately 1000 SD rats have been examined with a fundus camera or binocular indirect ophthalmoscope. Slight tortuosity of retinal vessels, prominant choroidal vessels and persistent hyaloid remnant were not uncommon findings in our laboratory control animals. Preretinal arteriolar loop, focal sacculation of retinal arterioles, preretinal hemorrhage, focal retinal atrophy, retinal detachment, and coloboma were also observed.