Purpose To observe the expression of proliferating cell nuclear antigen（PCNA）and bcl-2 of cultured human retinal pigment epithelial cells（RPE）． Methods SABC techniques were applied for immunocytochemical staining of cultured RPE with mouse anti-human PCNA monoclonal antibody and rabbit antihuman bcl-2 antibodies． Results 31.2% and 50.6% cultured cells were positive to anti-human PCNA at 24h and 48h after seeding，respectively．The positive staining was mottled in the nucleus．positive staining for bcl was seen in 76%to 90% cells as fine granules scattered within the cytoplasm. Conclusion One half of cultured RPE expressed PCNA，indicating that the cells were in phase S of the cell cycle．Positive staining for bcl-2 appeared in much more RPE cells．These biological markers may be associated with the growth activity of cultured RPE． (Chin J Ocul Fundus Dis,1998,14:26-28)