Cell proliferation mainly depends on cell cycles. p27(KIP 1) was cloned as a cell cycle inhibitor in 1994. In the retina, a variety of cells come to express p27(KIP 1) as development progresses, while the number of proliferating cells decreases. Human retinal cells show proliferation activity during embryonic stages, and subsequently differentiate into three neural retinal layers at the neonatal phase, when proliferating cells are no longer detected. The pathogenesis of retinoblastoma and proliferative vitreoretinopathy, major fundus disorders, is correlated with aberration of retinal cell proliferation. Recent research has shown that p27(KIP 1) plays important roles in this pathogenesis. In this review, we discuss the role of p27 (KIP 1) in retinal development, and in the pathology of fundus disorders. We conclude that the clarification of the mechanisms of p27 (KIP 1) expression might contribute to the discovery of a novel therapy targeting for human retinal diseases.