We used Mercury Analyzer to assess possible correlation between length and weight of the Kutum Roach (Rutilus frisii kutum) and mercury accumulation in different tissues of the fish. We collected fish specimens from central south Caspian Sea from October to December 2005. After biometrical measurement of samples and sex determination, mercury concentration was assessed in muscle, liver and skin tissues of the specimens. The mean concentration of mercury in muscle, liver and skin tissues was 849.9, 670.9 and 493.7ng/g respectively. Statistical analysis of the results showed a significant difference between mercury amounts in different tissues (P0.05). The mercury amount in muscle of Kutum Roach was lower than permissible limits proposed by FDA (1004ngig)