A 18-year-old male presented with ulcers of lips and tongue and erythema of trunk of more than a month duration. Laboratory examinations for syphilis showed that TRUST (+) 1:32, TPPA (+), and HIV antibodies were negative. Combined with his case history and signs, he was diagnosed with secondary syphilis with chancre of lips and tongue and was cured by injecting benzathine penicillin 2.4 million U into gluteal muscles on both sides once a week for three times. After a month, the erythema and chancre disappeared. Three months later, the TRUST test was positive, the titer was 1:8, and the TPPA was positive.