Antibodies against viral infection associated (VIA) antigen and against crude suspensions of strains "O1" Campos, " A Venceslau", "A24" Cruzeiro and "C3" Indaial of foot-and-mouth disease virus (FMDV) acquired by natural passive immunization were measured by the complement fixation test in buffaloes. Three animals were periodical tested for the presence of antibodies from birth to 6 mouths of age. The results showed that it is perfectly possible to measure antibodies against the VIA antigen and against the different strains of FMDV in buffaloes with a large safety margin, a characteristic that is not observed in cattle when the direct method is utilized.