Measurements of bioavailability responses in frogs from contaminated sites could provide valuable data for environmental risk assessment. Biomarkers are sensitive to both e nvironmental pollution and confounding factors that are not related to pollution. The specimens were collected on a monthl y basis from the Babol-River from July to September 2010 to determine if monthly changes exist in condition, he patosomatic index (HSI) and frogs. Fulton condition factor (FCF range: 1.513±0.431 – 1.638±0.473), hepatosomatic index ( HSI range: 3.901±0.504-5.231±1.206), Bioaccumulatio n factor (BAF), the highest level of copper was observed. Liver wei ght was seen to increase from July to August/Septem ber, most probably as a result of accumulation of metabolites, especia lly fat and glycogen. Furthermore, the concentratio ns of the metals found in the liver of the frog were in the order: Cu>Cr>C d>Pb>Ni. On the other hand, the concentrations of t he metals found in the water were in the order: Cu>Pb>Cd> Ni >Cr.
