*Örün, İbrahim ( Aksaray, Yazar )Neemazal-T/S is an organic pesticide that is a commercial form of azadirachtin (AZA). In this study, the common carp fish (Cyprinus carpio) was exposed to different concentrations of AZA (1.2 and 2.4 ppm) in acute (4 days) and subchronic (30 days) periods. The aim of this study is to evaluate the hematological, antioxidant and histopathological effects of AZA on carp. Total leukocyte count (WBC), granulocyte count, hematocrit (Hct), hemoglobin (Hb), mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) values were decreased in 2.4 ppm exposure whereas there was an increase in mean corpuscular hemoglobin concentration (MCHC) level and there wasn't any difference was found in monocyte ratios. In time-dependent comparisons; WBC, lymphocyte, granulocyte ratios, Hb concentration and Hct values were statistically significant in 2.4 ppm exposure in the subchronic period. Increase in malondialdehyde (MDA) levels and decrease in superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) enzyme activities in gill and liver tissues were found in both dose groups compared to the control group. Depending on the time, MDA level in subchronic period in both tissues were increased. Also depending on the time SOD, CAT and GPx enzyme activities in dose groups between both tissues were reduced. In gill tissues epithelial separation, flattening and shortening in the secondary epithelial lamellae and in liver tissues vacuolar degeneration, mononuclear infiltration and hydropic degeneration in the sinusoidal space histopathological defects were observed in subchronic period. Our study indicates that Neemazal-T/S has a toxicological effect on common carp hematological parameters, antioxidant enzyme system and histopathology
