Objective To study the ultrastructure of macular puck er (MP) from the patients with rhegmatogenous retinal detachment (RRD) and the mechanism associated with its development． Methods Twenty specimens of MP surgically removed by vitrectomy from 13 patients were dissected into two layers in each of them．The ultrastructure of two layers,i,e,near the vitreous and near the retina,was studied with electron microscopy． Results Seven sections of the near vitreous ones appeared prodominant collagen deposits and a few of epithelial like cells,and pigment particles might be present in the cytoplasm．While cells with foot processes were found in 13 membrane sections near the retina and increasing number of various types of cells rich in collagen around were observed including fibroblast like cells and glial cells． Conclusion The findings suggest that the MP after surgery of retinal detachment may possess a characteristic lamination,and posterior hyaloid cortex was involved in the developmetn of MP． The adhesion between posterior hyaloid cortex and macular area might be a key factor for forming MP． (Chin J Ocul Fundus Dis, 2001,17:52-54)