In the light of two recent cases of severe central nervous system malaria due to neglect in chemoprophylaxis, the authors report the very marked recrudescence in imported malaria and draw attention to the frequency of cases due to P. falciparum, the agent of malignant tertian fever and of malignant episodes. The necessity of early diagnosis in such cases is mentioned, together with the treatment of simple malaria and, in particular, of malignant varieties. In order to be effective, chemoprophylaxis must be begun immediately following arrival in an endemic area, continued regularly throughout the stay there and continued for 2 months after leaving. The blood of former malaria suffers, in order to avoid the risks of transfusion malaria, should be used only after seroimmunological studies have demonstrated the absence of anti-malaria antibodies.