Implementation conditions of the polymerase chain reaction (PCR) test were examined to determine its sensitivity, specificity, and repeatablity as a field method for diagnosing contagious equine metritis. The two-step PCR method, already reported on elsewhere, was used with some modifications. First, in terms of a DNA extraction method, Instagene Matrix was found to be slightly more sensitive to PCR than the boiling method and two other commercial kits. The PCR test detected all 30 strains of Taylorella equigenitalis isolated in foreign countries but did not react to 249 genital swabs taken from healthy horses uninfected by T. equigenitalis. PCR tests conducted in four separate institutions produced similar results. Our own results show that the PCR test is suitable for the diagnosis of contagious ermine metritis.