. Brugia malayi is filarial worm species that is widespread in Indonesia. It is also found in West Sulawesi, particularly in North Mamuju Region. The aim of this research was to describe the microfilarial periodicity of Brugia malayi. This study was conducted in Polewali Village, Bambalamotu District, North Mamuju Region, West Sulawesi Province in 2011. The periodicity study was conducted on the people whom microfilariae positive in their blood. The blood examination was conducted every hour in 24 hours. Night blood survey was collected at from 09.00 until 20.00 local time. Data were analysed using Aikat and Das formula. There were five positive Brugia malayi, with density peak of microfilariae (K) from 23.00'00'' until 01.27'.00'', the variety of microfilariae density (F) showed those cases have the circadian or harmonic, and the periodicity index (D) was more than 100%. The behaviour of Brugia malayi in Polewali Village, Bambalamotu Sub-district, North Mamuju Regency was nocturnal periodic.