The long-term effect of a single oral dose of 6 mg/kg bodyweight of diethylcarbamazine (DEC) combined with 400 mg albendazole (ALB) on the microfilariae (mf) of the lymphatic filarial parasite Brugia timori was studied on Alor island, Indonesia from April 2001 to April 2002. Before treatment the geometric mean of the mf density in 96 infected study subjects was 150 mf/mL night blood (range 1-5696 mf/mL). One year after treatment 69 subjects (72%) were mf-negative and the overall geometric mean mf density reduced to 3 mf/mL (0-2456 mf/mL). The reduction of mf was more pronounced 1 year after treatment compared with 6 months after treatment. It can be concluded that a single dose of DEC + ALB leads to a long-term and progressive suppression of B. timori mf for at least 1 year. Therefore, DEC+ ALB can be recommended as an effective strategy to control B. timori infection in the framework of the Global Programme to Eliminate Lymphatic Filariasis.