Morphological and cytochemical characteristics of neutrophil in Japanese amberjack, Seriola quinqueradiata were examined by light microscopy. The neutrophils were round to oval (7.0-11.0μm in diameter) and the nucleus round to lobule-shaped. Granules of the neutrophil were classified into three types； acidophilic granule (αG), chromophobic granule (βG), chromophobic granule (βG) and basophilic granule (γG). The αG was rod-shaped (0.5-1.0μm in length, 0.2μm in width) and stained with May-Grünwald (MG) stain. This granule was not observed in the preparations stained with Giemsa stain. The MG-Giemsa (MGG) staining pattern of the granule was influenced by pH and concentation of diluent of the staining solution. The βG was round to oval (≦0.5μm in diameter) and unstained by Romanovsky type stain (MG, Giemsa and MGG). This granule was alkaline phosphatase, peroxidase and sudan black B positive. The γG was round to oval (≦0.3μm in diameter) and stained with Giemsa and MGG, but not with MG. This granule was α-naphtyl acetate esterase positive. The Yasumoto body (Y-body) was also found in the neutrophil and toluidine blue positive.