To assess the clinical findings associated with detection of adult Wuchereria bancrofti worms on ultrasound, 186 schoolchildren in a filariasis-endemic area of Haiti underwent physical and ultrasonographic examinations. The filaria dance sign (FDS) of adult W. bancrofti was detected in the inguinal and crural lymphatics of 28 (15%) children. FDS detection was more common in older children (P = 0.003) and in those with a history of inguinal lymph node inflammation (P = 0.002) or crural lymphadenopathy on physical exam (P = 0.01). Twenty-five FDS-positive children were reexamined after three annual cycles of mass treatment for lymphatic filariasis (LF). The total number of adult worm nests detected by ultrasound decreased from 29 to 4 (P </=0.0001). FDS and lymphangiectasia were detected in the intrascrotal (N = 3) and inguinal (N = 1) lymphatic vessels of three postpubescent boys. This study demonstrates clinical and subclinical findings of LF in FDS-positive children.