Three human infections with an animal filarial parasite of a Brugia species have been identified in residents of New England over the past 2 years. All patients were asymptomatic except for local, superficial lymphadenopathy. The diagnosis was established pathologically by the finding of immature brugia worms in the biopsied lymph nodes. Peripheral blood eosinophilia was lacking; in one patient, no lymphocyte blastogenesis to filarial antigens and no antifilarial antibodies were detectable. These cases document a wider geographic range in the Northeast for this zoonosis, which had been previously recognized in two residents of the Middle-Atlantic states. The clinical and pathologic features resulting from the worm's intralymphatic localization and the structure of the brugia worm distinguish this entity from other zoonotic filarial infections.