Sera from 211 ostriches were tested for the presence of Newcastle disease virus (NDv)-specific antibodies by the virus neutralisation test, the haemagglutination inhibition (HI) test and a recently developed avian paramyxovirus serotype 1 (PMv-1) specific monoclonal antibody blocking ELISA (b-ELISA). The virus neutralisation test was used as the reference for the estimation of the sensitivity and specificity of the b-ELISA and HI tests. Of the 211 sera, 140 contained NDv-specific neutralising antibodies, 130 were positive by the HI test and 122 by the b-ELISA. The sensitivity, specificity and predictive accuracy of the HI and b-ELISA tests relative to the virus neutralisation test were similar. The good agreement between the HI and b-ELISA test (κ = 0.85) suggested that the two methods are interchangeable.