In the rat the first clinical signs of methylmercury intoxication is loss of appetite, which can be restored by the administration of dimercaptosuccinic acid (DMSA). In female rats which lost body weight as a result of methylmercury treatment, the anorexic effect of methylmercury was reversed even when DMSA was given in the drinking water. When intoxicated animals had the choice between DMSA supplemented water (2.5 mg DMSA/ml) and tap water, they preferred DMSA. This preference is related to the severity of intoxication and is abolished after one or two days. During this time the urinary mercury excretion is substantially increased and the body burden of methylmercury is decreased. The effect of methylmercury mobilization is fast, and can be detected in urine collected from cannulated ureters shortly after the IV administration of 10 or 20 mg/kg dimercaptosuccinic acid.