The presence of filariasis was investigated through Knott's method in 40 Curripaco Indians from communities located on the Casiquiare and Guainia Rivers in the Amazon Federal Territory of Venezuela. The results gave an 82.5% prevalence for infections with Mansonella perstans and 30% for infections with M. ozzardi (mixed infections with M. perstans). In almost all the patients the parasite load was greater for M. perstans and varied between 1 and 327 microfilariae per ml. This paper presents for the first time the presence of a transmission focus of M. perstans in the Amazon Federal Territory and confirms the finding of M. ozzardi in the region.