A blocking enzyme-linked immunosorbent assay (ELISA) developed for detection of antibodies to Actinobacillus pleuropneumoniae serotype 2 in sera from pigs (Nielsen et al., 1991) was evaluated for its suitability to detect antibodies in colostrum to this serotype. Using colostrum from sows experimentally infected with serotype 2 and from herds known to be infected with this serotype, the sensitivity of the test was 100%. Antibodies to A. pleuropneumoniae serotype 2 could be detected in colostrum of experimentally infected sows until at least 5 days after farrowing. Positive results were not observed with colostrum samples from herds known to be free from A. pleuropneumoniae. The high diagnostic sensitivity and specificity of the assay indicated that screening of herds for A. pleuropneumoniae serotype 2 infection by testing colostrum would be a reliable and simple method for herd monitoring.