Concentrations of lead, cadmium, and mercury in liver and kidneys of brown hares in relation to season, age, and sex were investigated. Over a period of one year 74 hares, 36 males and 38 females were analyzed. The concentrations of lead and cadmium were analyzed by AAS and mercury was determined by mercury vapor technique. The median concentration of lead in liver as well as in kidney in relation to the season is the highest in winter period in comparison with spring, summer, and summer period (p < 0.001). The highest concentration of cadmium was found in winter, but the differences were not significant. In mercury, we report significantly higher (p < 0.001) median concentrations in liver (0.023 mg kg(-1)) as well as in kidney (0.068 mg kg(-1)) in winter period in comparison with all other observed periods. In relation to age the concentrations in lead and mercury in liver and kidney were very similar, without significant differences. In cadmium we report significantly higher concentrations in the liver as well as kidney in adult animals (0.154 and 1.521 mg kg(-1)) in comparison with juvenile animals (0.048 and 0.582 mg kg(-1), respectively). In comparison of the female and male brown hares we found significantly higher (p < 0.05) median concentration of lead in the liver of males (0.216 mg kg(-1)) than in females (0.127 mg kg(-1)) and the level of cadmium is significantly higher (p < 0.001) in females (1.464 mg kg(-1) than in male brown hares (1.384 mg kg(-1)).