1,284 immoral persons and 1,161 healthy controls, from seven areas of China, were detected for the antibodies to Ureaplasma urealyticum (Uu), Mycoplasma hominis (Mh), and Chlamydia trachomatis (Ct) by indirect hemoagglutination (IHA). The results showed that: (1) in the immoral persons, the positive rates of antibody was the highest in Uu (25.47%), higher in Ct (18.22%), and lower in Mh (8.80%); (2) the levels of antibody to Mh, Uu, and Ct were significantly higher in the immoral persons than in the healthy controls; and (3) the immoral persons were commonly complicated with infections caused by Uu and Ct. It was indicated that the immoral persons were risk population of Mycoplasma and/or Chlamydial veneral diseases, and it must be noted for us controlling veneral diseases.