Insecticide Treated Nets (ITN's) offer good protection against malaria in Africa where the vector mosquitoes feed indoors late at night. However, in other parts of the world like South America, vectors feed earlier in the evening before people go to bed. In such cases it may be necessary to use alternative treatments in the evening to supplement the efficacy of ITN's. This study compares 2 matched groups of households in the Bolivian Amazon. One group will be given ITN's plus a plant-based insect repellent in the evening, the other has ITN's plus a placebo lotion. Households are monitored over a full malaria season to record numbers of malaria cases.