The traditional method of detection of microfilaria in night blood specimens for the diagnosis of Wuchereria bancrofti infection is being replaced with circulating filarial antigen in day blood specimens, which has a high sensitivity. However, both methods are indirect tests to detect the presence of adult worms in vivo. Localization of adult worms in vivo in their natural habitat may help in understanding better the end-point of drug treatment, the adulticidal action of antifilarial drugs, and in locating the site of lymphatic pathology. We used ultrasound examination to assess the preferential location of adult worms in an area endemic for lymphatic filariasis.