By using experimentally infected rabbits as a model for early syphilis, the applicability of in vitro DNA amplification was explored for detection of Treponema pallidum. It was determined that whole blood in heparin or EDTA (but not serum), lesion exudate, and punch biopsy as well as swabs of lesions are useful specimens for examination by the polymerase chain reaction. Swabs do not require special diluents, and the specimens, whether kept at room temperature or frozen, are well suited for use in the polymerase chain reaction.