The 'Great Pox', syphilis, is a systemic disease with many clinical manifestations caused by the spirochaete Treponema pallidium. It is usually transmitted sexually but congenital infections can occur and, in certain parts of the world, endemic nonvenereal disease due to T. pallidum exists. Controversy exists as to the historical origins of venereal syphilis. The most common theory, the 'Columbian Theory', is that Columbus brought it back from the New World in 1493. The second theory, or pre Columbian theory, is based on the fact that European medical literature in the 1200-1300s describes certain forms of 'leprosy' which were highly contagious, could be transmitted sexually and from mother to child in utero and were said to respond to mercury. This form of 'leprosy' may, in fact, have been syphilis. The least known theory, the Evolutionary Theory, postulates that the different Treponema spp. evolved from a single organism responding to changes in the environment. The first use of Salvarsan in 1909 was a breakthrough in the therapy of syphilis.