This study analyzes results of the presence of NADPH-diaphorase in neural structures of the pheasant spleen. The histochemical method of NADPH-d has been used as a marker of nitric oxide synthase (NOS). The NADPH-d positivity shows the specific sites of nitric oxide (NO), which is considered to be one of the new important neuromodulator. We have demonstrated the presence of NADPH-d positive nerve structures in the spleen of the pheasant. Nerve fibers and nerve cells have shown positively the reaction to NADPH-diaphorase. NADPH-d positive nerve fibres enter the spleen in the vicinity of blood vessels, gradually distributed in perivascular localization in the white pulp, reaching the central artery. NADPH-d positive nerve cells have been localized at the hilus of the spleen around splenic vessels. They were polygonal in shape and they occurred as solitary or numerous cells, forming ganglia. We have not found any NADPH-d positive nerve structures in both the red pulp and capsula. The presence of NADPH-d activity in nerve cells and nerve fibres suggests the utilization of NO in the spleen of the pheasant. (Fig. 4, Ref. 16.)