In this study, presence of M. hyopneumoniae which is the ethyological agent of Swine Enzootic Pneumonia was investigated bacteriologically and serologically in Turkey. For bacteriological investigation, lung tissue samples were obtained from 102 pigs, raised on a farm in Kırklareli district which is the only legal pig farm in Turkey. The pigs were slaughtered in Istanbul. For the determination of the seroprevalance of the disease, blood serum samples from 384 pigs raised in various districts including the match sera were analysed by ELISA. As a result of bacteriological examination, M. hyopneumoniae was not isolated from any of lung tissue samples. Specific antibodies against M . hyopneumoniae were detected from 214 of 384 pig sera by ELISA, and seroprevalance of the disease was calculated as 55.73 %.