SUMMARY
During 1976 - 1977, the Sabah Malaria Control Programme carried out an extended field trial comparing the residual effects of Summithiona, DDT and Malathionb against the primary vector of Sabah, An. balabacensis balabacensis Baisas in Kuala Penyu district. In the courseof this work and continuiting into 1978, a study was made of the conditions of increased malaria transmission in 3 areas four month after residual applications of Sumithion, DDT and Malathion. Since the findings relate to the southwestern part of Sabah which suffers annual anticipated seasonal outbreaks of malaria they are of particular epidemiological interest