Some serological diagnosis methods and examinations for detection of antibodies to sheep-associated malignant catarrhal fever (MCF) infection were investigated. The wildebeest-associated MCF virus strain WC11 propagated on fetal bovine thyroid cell cultures was used as an antigen. Antibodies were detected by complement fixation (CF) tests in cattle pathologically diagnosed as having sheep-associated MCF, as well as in cattle experimentally infected with MCF virus strain WC11. However, immunodiffusion precipitation was only detected in cattle infected with MCF virus strain WC11. The results of serological investigation by CF tests indicated that 64.3% of sheep possessed antibodies to MCF virus in the Hokkaido district of Japan and all serum samples which contained CF antibody titers greater than 1:4 had antibody titers larger than 1:8 in indirect immunofluorescence tests. The CF test we demonstrated here is available to quantitatively detect MCF virus antibody titers in epidemiological surveys.