Inarice farm infested with rice scum and treated with copper sulphate (CuSO4) for 10 days in concentration of about 2.5 mg/l, the reared Clari-as lazera (C.lazera) in this farm showed different biochemical deviations in their plasma and histo-pathological lesions in their tissues. Significant increases were presenicd in levels of plasma :tlucosc, tolal lipids and activilics of aminotransferases (AST & ALT) and alkaline phosphatase (ALP) after 2,4, 6,8 and lo days of CuSO4 treat- Values of plasma: total protein, total albumin and globulin exhibited significant decreases allo-ver the whole period of exposure to CuSO4 in the tice farm, and A/G ratios declined too at unpling times. Significant clevations were revealed in concen-rations of plasma creatinine, urca and uric acid at 2.nd, 4the and 6th days of exposure of C.lazera to CuSO4 in the rice farm, while, after 8 and 10 days of exposure, there were no ‘significant changes in these metabolites. In addition, levels of total biliruben in plasma had no significant changes along the whole pcriod of treatment. The histopathological cxamination of gills, liver, kidney, spleen and skeletal muscles of C.lazera of the present study exhibited degenerative and necrotic changes. The lesions showed slight alter-ations at the first days of treatment with CuSO4. Then, the degenerative and destructive changes increased and became intensive with time. At the end of exposure period the lesions appeared morc intensive and severe in addition to pronounced necrosis.