Laverania falciparum will grow in the liver of a chimpanzee and in the blood of a splenectomized chimpanzee. The tissue phase in the chimpanzee accords with previous descriptions in man, but the time of pre-erythrocytic development is a little longer in the chimpanzee. In the peripheral blood of a splenectomized chimpanzee L. falciparum was seen at all stages except the mature gametocytes. No second generation of exoerythrocytic schizogony or persisting exo-erythrocytic schizonts could be found in the liver 12 days after infection. On the basis of this and other evidence the choice is made to assign the parasite to the redefined genus Laverania.