The aim of the study is to determine the oxidative stress and inflammatory changes in naturally occurring canine visceral leishmaniasis (CVL). A total of 30 dogs, comprising 10 clinically healthy and 20 dogs with leishmaniasis were enrolled in this study. The diagnosis of canine visceral leishmaniasis was performed by the immune fluorescence antibody test with antibody titter >= 1:128 and lymph node smear examination. In blood samples of dogs with visceral leishmaniasis, levels of malondialdehyde, total antioxidant capacity, glutathione, nitric oxide, myeloperoxidase, adenosine deaminase and cytokines (TNF-alpha, IL-1 beta) were determined and compared with the healthy controls. Significantly high levels of plasma malondialdehyde, nitric oxide, myeloperoxidase, adenosine deaminase and cytokines and significantly low levels in total antioxidant capacity and glutathione levels were found in dogs with leishmaniasis when compared with the healthy controls. According to the result of this study, oxidative stress and inflammatory changes occur in CVL. And this is the first report for myeloperoxidase (MPO) activity in CVL. Therefore investigation of this enzyme activity in dogs with leishmaniasis may be used for the diagnosis and inflammatory changes in dogs with VL.