Treponemal diseases comprise venereal syphilis (Treponema pallidum subsp. pallidum) and the endemic (non-venereal) treponematoses, i.e. yaws (T. pallidum subsp. pertenue), endemic syphilis (T. pallidum subsp. endemicum) and pinta (T. carateum). Treponemal diseases are distinguished on the basis of epidemiological characteristics and clinical manifestations. They are at present indistinguishable by morphological, immunological or serological methods. Several minor genetic differences have been identified among the subspecies. The endemic treponematoses have not yet been eliminated and are currently thought to affect at least 2.5 million persons. Renewed action towards the elimination of these diseases should be undertaken.