Abstract： A 77-year-old male patient was admitted to the hospital for chest distress, depression, drowsiness, edema of lower limbs, anepithymia, debilitation and scaled erythema on the limbs and trunk. Sera, cerebrospinal fluid and pleural effusion were obtained from the patient and subjected to the detection of antibodies to Treponema pallidum with rapid plasma reagent test (RPR), Treponema pallidum particle agglutination assay (TPPA) and Tp-IgM-ELISA. Both the sera and pleural effusion were positive for RPR with a titer of 1∶128 and 1∶64 respectively, as well as for TPPA and Tp-IgM-ELISA test, whereas the cerebrospinal fluid was weakly positve for TPPA but negative for the other two tests. Serologic tests can be utilized to detect the antibodies to Treponema pallidum in pleural effusion.