 Syphilis and HIV are prone to occur concomitantly and the two diseases share several modes of acquisition and risk factors such as men who have sex with men MSM, sexual workers, intravenous drug users, previous history of sexual transmitted diseases STDs, and multiple partners. HIV infection rates of up to 50 have been reported among patients diagnosed with syphilis in several regions, with higher HIV infection rates among MSM. Besides, syphilis ulcers are proposed to enhance the transmission of HIV. In Taiwan, there is also an increasing prevalence of syphilis and HIV co-infection among MSM. Therefore, to treat syphilis is an important issue for public health. 