The authors' light and transimission electron microscopy examination of the X-organ (XO)-sinus gland (SG) complex in adult cultured Chinese shrimp (Penaeus chinensis) revealed that its SG was composed of inner sinus and outer sinus and located on the lateral side of the medulla interna and dorsal medulla terminalia separately. Only one cell type like neurosecretory cells was found in the medulla terminalia. Transimission electron microscopic examination revealed that the SG was mainly composed of enlarged axon terminals abutting on the thin basal lamina of a central hemolymph lacuna acting as a storage release centre for the membrane bound neurosecretory material. Also present in the SG were glial cells with cytoplasmic processes which enwrap the terminals. Four types of neurosecretory terminals were distinguished on the basis of size, morphology and electron density of the neurosecretory granules. Each axon terminal contained only 1 type of granule; the mean granule diameter ranged from 137 nm (type 4) to 236 nm (type 1). Neurosecretory granules exocytosis was not observed in the SG of the Chinese shrimp. To our knowledge, the villus originated from the lamina was not found in the SG of crustaceans dispite of Chinese shrimp, some images showed that villus were related with the releasing of granules from the neurosecretory granules. Examination of the SG ultrastructure showed the existence of four kinds of neuropeptides that could be separated from the SG extraction by high performance capillary electrophoresis in 50 μm i.d. X 37 cm (33cm effective length) amino-coated capillary, with 0.1 mol/L boracic acid buffer (PH 8.0) as running buffer at 18℃ and 6kv running voltage[(-)-(+)].