The use of the indirect fluorescent antibody test and complementary blood smear examinations in Colombia has shown that Trypanosoma vivax infections of cattle may be considered to be distributed throughout the tropical and subtropical areas of the country. However within this distribution the prevalence showed wide variations between herds and localised epidemic situations could occur at the herd and village level. the examination of sequential serum samples from 2 localities has given additional information on incidence and on transmission patterns.