This finding is in line with some previous studies that have been done in TTS. Nahak (2000) found that the peak of malaria incidence was from June to August. Haryani and Mortono (1991, cited in Nahak, 2000) found that July, August and October had the highest density of An barbirostris, the main vector of malaria in Timor Island. Gundefinger (1975, cited in Nahak, 2000) also has given a similar pattern of malaria transmission in Besikama, Belu District as in TTS District. Besikama is one sub district which is located on the border of Belu and TTS District.