A commercial ELISA test to detect serum anti-gE antibodies to Aujeszky's disease virus was adapted for use with muscle exudates. The muscle samples were taken from the diaphragm of pig carcasses at the slaughterhouse. Three hundred and eighty-nine pairs of samples of serum and muscle exudate were compared to determine the possibility of using muscle exudate samples in a programme to control Aujeszky's disease. Taking the serum samples as the reference, the individual sensitivity of the test was 93.2 per cent and the individual specificity was 98.3 per cent. The concentration of antibodies in the muscle exudates was on average 20 times lower than that in the serum samples.