Syphilis is a disease, usually sexually transmitted, caused by infection with the spirochete Treponema pallidum (T. pallidum). Infection is systemic from the outset and the disease is characterized by periods of latency, often in excess of twenty years. These features, together with the fact that T. pallidum often cannot be isolated in culture mean that serological techniques play a major role in the diagnosis of syphilis and treatment follow-up.