The present study estimated oxidant/antioxidant status in blood of sheep naturally infested with Haemonchus contortus. Blood samples from infected and healthy (control) sheep were used to determine hematological, some antioxidants and biochemical parameters. The sheep showed microcytic hypochromic anemia. Haemonchosis in sheep resulted in a significant stimulation in MDA & PC. By contrast, a significant inhibition of the antioxidants activity of both SOD and GSH coupled with a significant inhibition of both ceruloplasmin (CP), Total Iron (Fe) and Copper (Cu) in infected sheep. In turn, a significant stimulation in CAT activity and in TFAA in infected sheep compared to control values was detected. The results showed a significant positive correlation between the increasing level of PC with the stimulating levels of MDA (r=0.47, R2=0.22, P=0.02), CAT activity (r=0.60, R2=0.37, P=0.001), TFAA in plasma (r=0.46, R2=0.21, P=0.03)
and EP (r=0.43, R2=0.19, P=0.04). By contrast, stimulated level of PC was inversely correlated with diminished values of SOD (r=-0.55, R2=0.31, P=0.03), Hb (r=-0.43, R2=0.19, P=0.04) and PCV% (r=-0.65, R2=0.42, P=0.003). Haemonchosis was accompanied by disturbances in protein synthesis and a general oxidative damage.