If you have had sexual contact, i.e., high-risk contact, with a person with syphilis or with a person with latent syphilis, at which point you are at risk of contracting syphilis, it is recommended that you get tested for syphilis within 2-4 weeks. Because the incubation period of syphilis is 9-90 days, with an average of 3 weeks, most patients begin to develop syphilis 2-4 weeks after infection. A negative syphilis serologic test 15 days after high-risk sexual contact does not yet rule out the possibility of syphilis infection. Serologic tests for syphilis include both specific and nonspecific antibodies. Specific antibodies, such as TPPA, are indicators of syphilis infection, and it generally takes 2-4 weeks from infection for the body’s immune system to develop these antibodies. Specific antibody tests cannot distinguish between current or previous infection and need to be combined with the non-specific antibody TRUST titer to determine how active the virus is. Therefore, a negative syphilis test 15 days after high-risk sex does not exclude the possibility of infection, and a syphilis serologic test is needed within the next 2-4 weeks for review. After three months of high-risk sex, a negative syphilis test can rule out the possibility of infection.