Objective To investigate the expression of costimulatory molecules, Fas/FasL, and major histocompatibility complex (MHC)-class II antigens in normal ocular tissues. Methods Twelve eyes were obtained from the eye bank of Zhongshan Ophthalmic Center within 16 to 24 hours postmortem. Six eyes were used for making the retinal wholemounts, and the tissues (iris and ciliary body, choroid, and retina) of the others were used for making the frozen sections. Immunohistochemical staining was carried out on these retinal wholemounts as well as on tissue sections to investigate the exprenion of B7-1 and B7-2 (costimulatory molecules), HLA-DR(MHC class II), CD68 (macrophages), Fas/FasL. Results The results of immunohistochemical staining showed the presence of B7-2, FasL, CD68 and HLA-DR in the iris and ciliary body. Expression of B7-1, FasL, CD 68, and HLA-DR was found in the choroid while HLA-DR, CD68 and FasL were detec table in the retina. Conclusion Expression of costimulatory molecu les, MHC-class II molecules and molecules related to apoptosis is different in the iris, ciliary body, choroid, and retina, which may play an important role in the stability of the immunological microenvironment of these tissues.(Chin J Ocul Fundus Dis，2003，19：109-112)