Abstract: Chemical analysis of surface water samples collected randomly from three locations in lake Maryut indicated a considerable rise of certain heavy metals and bad water quality in polluted locations (Moharrem Bey and Merghim basin), with elevated chemical and biological oxygen demands (BOD) as compared to reference area (Fish farm) characterized with lesser metal content, water turbidity and alkalinity. Cytochemical changes in glycogen, proteins and lipids content in liver of Tilapians caught from these locations were investigated. Hepatocellular accumulation of protein and lipid inclusions in association with depletion of glycogen appeared in the polluted specimens. In parallel, enhanced levels of total proteins, total lipids, cholesterol, glucose and creatinine were estimated in blood of fish inhabiting the polluted areas. It can be concluded that biochemical parameters that fluctuated in response to deleterious effects of pollution could be ranked as possible biomarkers of pollution. This study also underlines the importance of morphological studies as a link between biochemical-physiological and ecological investigations.