The prevalence of Mansonella ozzardi in the Comisaría del Vaupés of eastern Colombia was investigated as part of an extensive study of human filariasis in Colombia. Three hundred and forty-seven individuals from various parts of Vaupés were examined. The overall infection rate for M. ozzardi was 49%, but the distribution of the parasite was not uniform throughout the Comisaría. Microfilariae were found in both venous blood samples and ski biopsies of infected individuals. The rate of infection was 55% for males and 42% for females, and infection ratenerally low, with 88% of the positive films having less than 50 microfilariae.