After the successful identification of Borrelia burgdorferi as the cause of Lyme disease, a new tick-borne infection occurring in the United States, almost identical spirochaetes have been isolated from the tick Ixodes ricinus in Europe. As a result, the spirochaetal aetiology of skin diseases, which had long been recognized as tick-borne infections, namely erythema chronicum migrans with its neurological complications of the tick-borne meningopolyneuritis of Garin-Bujadoux-Bannwarth, acrodermatitis chronica atrophicans and lymphadenosis cutis benigna, could be confirmed by means of microbiological, histological and serological methods. On the basis of case histories it had already been assumed for some time that anetodermia maculosa and the localised sclerodermas might also be caused by a tick-borne agent. The results of serological investigations have now strengthened this assumption, although microbiological confirmation is still lacking.