The effects of intra-peritoneal injection of inorganic mercury on haemato-logical parameters and hepatic oxidative stress enzyme activities were studied in common carp, Cyprinus carpio. The fish were injected thrice intra-peritoneally with mercuric chloride TEX>$(5,;10mg;Hg;kg;b.W.^{-1})$</TEX>. After exposure of three different mercury concentrations a physiological stress response was exerted on C. carpio by causing changes in the blood status such as erythropenia in blood and oxidative stress in liver. Red blood cell counts, hemoglobin concentration and hematocrit level were reduced in most cases by inorganic mercury. Remarkable low level of serum chloride, calcium and osmolality were also observed in the mercury- exposed fish. However, serum magnesium and phosphate were not altered by exposure to mercury. An increased activity of hepatic glutathione peroxidase was observed in the lowest treatment group of carp $(1mg;Hg;mg;b.w.^{-1})$, hence, hepatic catalase and glutathione peroxidase of carp exposed to higher concentration of mercury $(5,;10mg;Hg;kg;b.W.^{-1})$ showed significant reduction in such activities.