Summary:Pathological findings in spirocercosis encountered in a female, 7 months old, mongrel dog which was found dead in a heavily forested area and brought to the Pathology Department of Veterinary Medicine Faculty of Ankara University to be necropsied with toxication suspicion by the Directorship Branch Office of Nature Protection and National Parks of Ankara Province are described. At necropsy, 23 independent, 0.8-1 cm diametered nodules which were hard in consistency and showed ash-gray whitish color and had red string-like material in the center of the cut surface that were diffusely located on mesenterium mainly close to curvatura major of the stomach are observed. At jejenum, under serosa another nodule with the same characteristics is seen. Another three masses that were able to be seen even from the serosa of the stomach are encountered. At the part of aorta that is close to the apertura thoracis cranialis numerous nodules with the same characteristics are found. In histopathological examination of the nodules that were taken from aorta, mesenterium, stomach and the intestine, granulomas consisted of parasite (Spirocerca lupi) in the center and was surrounded by necrotic tissue and cellular infiltrations of mainly eosinophil and neutrophil leukocytes with plasma cells, macrophages and lymphocytes are observed in tunica adventitia of aorta, under serosa in the intestine and mesenterium as solid nodules. It is also observed that cellular infiltration was surrounded by connective tissue.