Abstract: Tengxian County was a hyperendemic area of bancroftian filariasis, with a micro-filaria rate of 25.3% in the population before control measures were taken, and it has now dropped to 0.17% as a result of repeated treatments and DEC medicated salt administration to 1.4 million inhabitants.In 1983, a total of 1,355 patients with clinical manifestations of bancroftian filariasis were found in different parts of this county, including 172 cases of elephantiasis, 698 with hydrocele, 411 with chyluria and others. Among the 172 elephantiasis patients, 169(98.3%) were old cases, only 3 newly occurred cases(I stage). Most of the hydrocele cases were mild. The incidence of chyluria raised significantly in late years, its cause being discussed.