The pathological effect due to effect of petroleum hydrocarbon on common carp Cyprinus carpio and then reflected indirectly on human health was studied. Seven groupsof fish were exposed to seven different concentrations (0.04,0.08,0.12,0.16,0.20,0.24,0.28)ml100ml consequences , the eighth group was left as control group (without addition) The fish was observed for 72 hours to detect the non killed concentration (LC0),the concentration kill half (LC50) and concentration killed to all (LC100) (0.20,0.24,0.28)ml/100ml respectively . A group of fish was exposed acutely to the concentration (0.20) that does not killed. The fish carried to another aquarium contain tap water and watched for seven days after that we take tissue sections from the exposure fish organs (liver, intestine , muscles, gills, brain, kidney ).The samples was diagnosed Histopathologically, The Results showed an appearance of pathological signs represented by nervous signs, abnormal swimming produce by toxic effect on the central nervous system and histopathological changes represented by congestion of blood vessels, perivascular inflammatory cuffing chronic type in addition to vaculation of the cell and single cell necrosis in some of them