Mefloquine (WR 142-490, RO 21.5998), and antimalarial 4-quinoleine-methanol, active on multiresistant strains of P. falciparum is a resourceful product because of its pharmacocinetics and the possibility it opens of a single day curative therapy. Its mean half-live is 15 days, with important individual variations from 8 to 23 days as well as racial one within North-American, Asiatic or African patients. A 1,25 to 1,50 g dose divided in 2 or 3 intakes during 16 hours has proved to be effective in 34 P. falciparum cases. Lower doses, near 1 g seem sufficient for P. vivax (6 cases) and P. ovale fits (4 cases). Clinical and biological acceptance are good, according to this limited study. The use of mefloquine might nowadays be reserved for geographical areas where resistance to P. falciparum is significantly high. Its diffusion in Africa, south of the Sahara, though conceivable, might be discarded for the time beeing.