SIR,-I was glad to read a letter from Dr. Copeland (Dec. 6), a pioneer in bringing medical treatment to the Muruts of North Borneo.1 I feel that something should be said about the present malaria situation there. McArthur's control measures for the vector " Anopheles leucosphyrus " (now A. balabacensis), were in fact resumed by him under the new post-war Government. Clearing the undergrowth around seepages was tried during 1949-52, and showed some reduction in vector breeding and spleen-rates.2 However, more recent surveys have shown that McArthur's experimental villages no longer show any malariometric advantage over comparison villages, despite his hopes for the relative permanence of his methods. It was decided by the GovemmentjW.H.O.jUNlcEF Malaria Project to use house spraying with residual insecticide, which had proved highly effective in Sarawak against the virtually identical A. leucosphyrus. For Dr. Copeland's information, these mosquitoes do rest on walls during the night for periods sufficiently long to make them susceptible to effective attack by residual insecticides. It has been shown during the past three years that residual insecticides produce a very great decrease in the density of the vector. On Labuan Island house-spraying alone has been successful in interrupting transmission, and when combined with antimalarial drugs it has been shown capable of controlling transmission even in the most difficult parts of the interior. The complete eradication of malaria from British North Borneo now appears to be an attainable goal.