BACKGROUND.Lymphatic filariasis(LF) is one of the major public health problems in Indonesia. All three types of lymphatic parasites namely Wuchereriabancrofti, Brugiamalayi and Brugiatimori are prevalent in Indonesia. An estimated 125 million people are at risk of filariasis infection, in 337 endemic districts. In Kota BesiSubdistrict there was 51 cases mfpositif, two of them less than 15 years old. Distribution of the disease tends to spread in rural areas and epidemiological dataesspecialy periodicity is needed to eliminated this disease. AIM. The research aims to find the periodicity of microfilariae in human patients. METHOD. This research conducted in Kota Besi Sub District, KotawaringinTimur District, Central Borneo Provoince. This is Observational Study with 386 sampel. Examination parasite with Thick blood smear technique and blood is taking at night (08.00 pm– 06.00 am). If a sample positifmicrofilaremia a respondent blood will be taken again to know the periodicity of microfilariae in their blood. Determining of periodicity with Aikat and Das method to calculate a peak of microfilaremia density. RESULT.Four person of 386 is mf-positive were examined by the fingerprick method. Brugiamalayi was found in four person mf-positive, microfilariae periodicity in this location isnocturnal periodicwith harmonic waves and nocturnal sub-periodic with the non harmonic waves. Conclusion.Lymphatic Filariasis in Kota Besi caused by Brugiamalayiand periodicity is nocturnal and sub periodic nocturnal. Sub-periodic nocturnal is zoonosis so the elimination is different with the anotherspesies of filariae helminth.