Serological tests for syphilis are of fundamental importance in studying treponemal infections in experimental animals. Non-human primate species have been increasingly employed in treponematology in the past few years. However, Fribourg-Blanc, Niel, and Mollaret (1963, 1966) found an endemic treponeme in cynocephalus monkeys from Guinea. Sepetjian, Guerraz, Salussola, Thivolet, and Monier (1968) noted that 85 per cent. of twenty monkeys from an endemic yaws area in Africa had reactive FTA-200 tests. Furthermore, Kuhn, Brown, and Falcone (1968) observed that 15 per cent. of 250 normal chimpanzees had reactive serum FTA-ABS tests. During the past 6 years, our laboratory has used owl monkeys (Aotus trivirgatus), squirrel monkeys (Saimiri sciurea), and marmoset monkeys (Tamarinis nigricollis) in the investigation of ocular and neurosyphilis. The purpose of this report is to review the serological findings in the VDRL, RPR, TPI, FTA Buffered Saline (BS), and FTA-ABS tests in 151 normal primates of these three species.