PURPOSE: To investigate the activation and immune respones of lymphocytes in epiretinal membranes (ERMs)and subretinaI membranes (SRMs). METHODS: A panel of morioclonal antibodies against CD23 (activated B cell), CD25 (activated T cell), CD68(macrophages) and HLA-DR (human leukocyte antigen II antigen)were used for the study of 20 specimens of ERMs from 20 patients with proliferative vitreoretinopathy (PVR),traumatic PVR and secondary traction retinal detachment,and 2 SRMs from PVR and traumatic PVR, with positive and negative reaction specimens as controls. RESULTS:Four cases of ERMs were found to be CD23 and CD25 positive respectively,and one case of SRMs to be CD23 and CD25 positive respectively. All the specimens of ERMs and SRMs revealed CD68 and HLA-DR positive in this series. CONCLUSIONS :There might be an aberrant immunoreaction mediated by T and B cells in the ERMs and the SRMs,and they might play an important role in the patbogenesis of PVR,traumatic PVR and secondary traction retinal detachments. （Chin J Ocul Fundus Dis,1996,12: 147-150）