A hybridoma cell line secreting monoclonal antibody (McAb) against Brugia malayi adult worm excretory-secretory antigen (AWES) was established. The identification of the Ig sub-classes showed that McAb AWES belongs to IgG. We developed a Dot-enzyme-linked immunosorbent assay (Dot-ELISA) to detect circulating parasite antigens in human lymphatic filariasis. 75 of 77 (97.4%) bancroftian microfilaremia cases showed positive reaction. 27 out of 40 (67.5%) microfilarial patients with hydroceles, chyluria, or elephantiasis, and 20% of sera from asymptomatic residents of filariasis-endemic areas evidently contained filarial antigens. 31 of sera from non-endemic area with ascaris infection were all negative. The minimal amount of antigens in pool normal sera adding AWES antigen was detectable at 6.3 pg/ml. The results suggested that Dot-ELISA is a sensitive, specific, cheap and simple agent for use in epidemiological field studies.