One hundred and twenty thoroughbred breeder mares with endometritis or infertility were investigated for the detection of antibodies to Taylorella equigenitalis by the passive haemagglutination (PHA) test and ELISA between 1997 and 1999 in the Marmara region and the two tests were compared. Fifty-eight (48.33 %) of 120 sera were found to be positive by the PHA test and 52 (43.33%) by ELISA. 22 of the sera were found to be positive by the PHA test reacted at 1/64 titer, 27 at 1/128, 7 at 1/256 and 2 at 1/512 titer. Sera from 44 mares were positive in both tests. Amongst these, 14 sera were positive in the PHA test and 8 sera were positive in ELISA. The difference between the PHA test and ELISA positivity was 8% and this was not statistically significant. In conclusion, the PHA test was recommended for routine screening of CEM because of its easy handling and rapidness.