[Seroepidemiological investigations on the prevalence of chlamydial antibodies in the human (author's transl)].

1,075 serum samples taken at random from blood donors and 524 samples from patients were investigated with a group-specific antigen for chlamydial antibodies. Antibodies were detected in 9.9% of the blood donors and in 25.7% of the patients, with titers from 1:5 to 1:160 in the former group and up to 1:640 in the latter group. In general, patients had significantly higher titers than blood donors. More attention should therefore be paid to the possible role of Chlamydia in infections of unknown origin.