Anti-Th/To autoantibodies have been recognized as serological markers of systemic sclerosis (SSc) for more than 20 years. However, validated immunoassay kits to test this specifi city have not been commercially available. SSc autoantibodies are basically mutually exclusive and are associated with a certain subset of the disease and/or with organ involvement. Anti-Th/ To are generally considered to be markers of the limited cutaneous type of SSc with the involvement of certain internal organs. The excellent correlation between anti-Rpp25 as detected by their novel chemiluminescent method and anti-Th/To as detected by immunoprecipitation suggest that the new assays may become widely available tests for clinicians in future and could help to clarify the clinical signifi cance of anti-Th/To in SSc as well as other conditions over different races or countries.