Buffalo sperm fertilizing capacity principally depends on sperm motility and membrane integrity. Peroxidative damage induced by Reactive   Oxygen Species (ROS) has been proposed as one of the major causes of defective sperm function. The objective of the present study was to investigate the presence of superoxide dismutase (SOD) in the buffalo semen and its role in the defense against oxidative damage. Fifty semen samples were collected from 16 buffalo-bulls (4 - 15 years old) and evaluated before cryopreservation. The activity of SOD and glutathione-S-transferase (GST) as well as the levels of glutathione (GSH) and malondialdehyde (MDA) were assayed in the seminal plasma before freezing. Aspartate amino-transferase (AST) and cholesterol contents were assayed in seminal plasma before freezing and alter freezing- thawing. The results revealed the presence of SOD activity (0.07 ± 0.01 U/mg protein) in the seminal plasma of buffalo-bulls. The increasing SOD activity accompanied high sperm motility after dilution and before freezing. Semen evaluating parameters varied with the age of bulls and high values were found in young than old aged animals. Positive correlations existed between activities of SOD and GST in the seminal plasma and inverse relations were detected between SOD activity and both cholesterol efflux and frequency of post-thaw sperm cell abnormalities. The relations between post-thaw sperm cell abnormalities and each of MDA, AST and cholesterol were positive. The rate of in-crease in post-thaw sperm motility in response to 5 mM pentoxifylline was high in samples with low MDA level before freezing.