Objective To compare the thickness of the retina and its sublayers between young and elderly rats using a stereological method. Methods Six young(3 months old) and six elderly(2 year old) Long-Evans rats were used in this study. The right eyeball was dissected from each rat and prepared as a set of serial sagittal sections and applied with HE staining. The sections and fields were sampled in the systematic random fashion and examined under a light microscope. The thickness of the whole retina and its 8 sublayers were identified and measured. Results Compared with that of the young rats, the thickness of the whole retina and most of the sublayers of the elderly rats were significantly decreased. The decrease was such so that the proportion of the thickness of each sublayer to that of the whole retina remained unchanged. Most interestingly, among the 8 sublayers of the retina, the thickness of the exterior plexus layer reduced nearly 462% during aging process.Conclusion Aging has a significant effect on the thickness of the rat retina. Such effect is better presented with the systematic random sampling method