In this study embryonic development of Chicken Bursa Fabricii (Avian cloacal bursa) was investigated by light microscopy. For this purpose 1 50 fertilised eggs of a domestic hybrid line, GXSX were used as a material. From 6th to 17 th days of hatching, 5 of embryo containing eggs were opened each day and tissue samples were taken. Following fixation in alcholic-formaline or Helly fixatives, the tissue samples were immersed in paraffine blocks by means of common histological techniques. Tissue sections taken at 6µm in thickness were stained with Crossman's trchrome and Pappenheim's panoptic staining methods. Primordial bursa with a centrally located lumen was first observed on the 7 th day of hatching. Lymphoid follicle development started on 10 th day when large, basophylic mesenchymal cells migrated underneath the epithelial layer of the central lumen. The follicles have completely formed and gained organ-spesific organization by the 17 th day of hatching. In the surface epithelium of the organ, follicle associated epithelium (FAE) and interfollicular epithelium (iFE) were distinguished. Follicular medullae have been surrounded by a definite cortico-medullar cell line. The coitico-medullar epithelium, which is endodermai origin, constituted the subnodular epithelium (Sne) during the follicular development.