Female albino mice with a weight ranging from 18 to 20 g were given varying doses of Pyrvinium-Pamoat orally. The DL50was reached at 95 mg/kg body weight when applied once. The animals deceased spontaneously and those killed afterwards were examined both macroscopically and histologically. The result was that the therapeutic dose of 5 mg/kg body weight used for man did not cause any pronounced pathological changes either in the liver or the kidneys. Those animals, however, which were given much higher doses showed a temporary, dim swelling and fattening of the liver- and tubulus epithelia dependent on the dose applied, which revealed a distinct decrease after only 3 days and did not last for more than 6 days.