The prevalence of chlamydiosis in pet dogs was surveyed in Shenzhen,Guangdong Province,China.A total of 442 serum samples were collected from three districts of Shenzhen,namely the Futian,Nanshan,and Luohu Districts,and assayed for Chlamydiaceae antibodies by indirect haemagglutination assay.The results showed that the mean positive rate was 6.11%,and the positive rate for the Futian District was the highest(9.52%),followed by the Nanshan District(7.08%),and the Luohu District(4.02%).The positive rate for male dogs was 6.08%,and for female dogs 6.16%.Out of all the 38 breeds of dogs examined,14 breeds were positive.The positive rate for the Cocker Spaniel dog was the highest(14.2%),followed by the Pekinese dog(10.71%),and the Border Collie dog(10.34%).This is the first time that the seroprevalence of Chlamydiaceae infection in pet dogs in Shenzhen,Guangdong province,China was reported,and the results indicated that pet dogs may be an important source for human infection by Chlamydiaceae in Shenzhen and other areas of China.