In the present study our major aim was to evaluate the up-to-date contamination status of the Topolnitsa reservoir. It is located in a region with intensive copper mining, which has been constantly contaminated with metals in the last few decades. Thus, we measured As, Cd, Cu, Ni, Pb, and Zn concentrations in surface water samples, as well as, in liver of.ommon carp in three different seasons spring, summer, and autumn 2013. Furthermore, we also studied the carp response to the water quality by observing its hepatic morphological structure and measuring some biochemical parameters (LDH, ALAT, and ASAT activity). In general, metal concentrations in the water varied, but As, Cu and Ni were present in all the three seasons. Cu concentrations were above the maximum permissible levels set by law. Metal concentrations in the liver were significantly higher than in the water (p<0.05). In addition, we observed severe hepatic histological alterations, which included degenerative changes - granular degeneration, vacuolar degeneration, hydropic degeneration, and fatty degeneration; necrotic changes (necrobiosis) karyopyknosis, karyorrexis and karyolysis, and necrosis; and changes in the blood vessels - hyperemia in sinusoids and major blood vessels. We found that LDH activity was inhibited in the common carp liver from the Topolnitsa reservoir compared to the reference fish, but ALAT and ASAT activity was significantly increased compared to the reference. Based on our findings we consider that the metal-contaminated waters of the Topolnitsa reservoir lead to negative changes at tissue and cellular level in the fish organism, which include altered structure and impaired functions of the liver.