Objective Peritoneal lymphatic features are studied to provide necessary data for understanding transport capabilities of the endothelial and mesothelial cells. Methods Enzyme\|histochemical staining methods were employed to investigate organization of the lymphatic networks and their endothelial ultrastructures in the monkey peritoneum using light,scanning and transmission electron microscopy. Results 5' Nase positive initial lymphatics showed extensive network,obvious valve like structures and numerous blind ends.The calibre of lymphatics with extremely irregular lumen varied greatly from 40 to 120?m.Lymphatic endothelium was usually separated from mesothelium by a small quantity of loose connective tissue,or they directly contacted each other in some areas.No basal lamina occurred between the peritoneum and the lymphatics originating from milky spots in the omentum and mesovarium.Milky spots are oval or round visible bodies aggregated by macrophages and lymphocytes.Both the endothelium of lymphatic lacunae and the mesothelium that forms the peritoneal stomata,represent a strong 5' Nase activity.Abundant microfibrils attached the stomatal edge. Conclusion The distribution and structure of peritoneal initial lymphatics reveal significant regional variations,and lymphatic endothelium has a close morphological and functional relationship with the mesothelium. [