This work, carried out on a rubber estate in Malaya during 1949, was a Continuation of the trials begun in 1948 previously recorded [this Bulletin, 1949, v 46, 1116]. Full details concerning the terrain and the nature of the experiment were given in the previous publication. In 1949 the malaria rate in the area approached the rates which were customary in pre-war years, for the first time since the reoccupation of the country. The Indian population which was chosen for the experiment contains the survivors of the Japanese occupation; many had been in Siam and almost all had suffered from malaria. Treatment had been entirely lacking or very inadequate, with the result that the survivors had developed a high degree of immunity by the end of the war. These facts probably explain the low incidence of malaria in post-war years in spite of high prevalence of A. maculatus. No anti-larval measures have been carried out since 1941. Neo-premaline completely suppressed malaria in one group, the control group showing a high incidence. In other groups chloroquine, or chloroquine and pentaquine combined, given once a week, promptly brought to an end primary waves of malaria which were rising rapidly.