Morphological and cytochemical characteristics of neutrophil in Japanese eel, Anguilla japonica were examined by light microscopy. The neutrophils were round to oval (9.0-14.5μm in diameter) and the nucleus round to lobule-shaped. Granules of the neutrophil were classified into three types； acidophilic granule (αG), chromophobic granule (βG) and basophilic granule (γG). The αG was round to oval (0.3μm in diameter) or rod-shaped (≦1.0 μm in length) and stained with May-Grünwald (MG) stain. This granule was not observed in the preparations stained with Giemsa stain. The βG was round to oval (≦0.6μm in diameter) and unstained by Romanowsky type stain (MG,Giemsa and MG-Giemsa (MGG)). This granule was peroxidase positive. The γG was round to oval (≦0.3μm in diameter) and stained with Giemsa stain. Some enzymes, such as acid phosphatase, α-naphtyl acetate esterase and α-naphtyl butyrate esterase were detected in the γG. The Yasumoto body (Y-body) was also found in the neutrophil and toluidine blue positive.