Some connective tissue diseases are characterised by specific autoantibodies. Although anticentromere or antikinetochore antibodies (ACA), and antitopoisomerase-I or anti-Scl-70 antibodies (ATA), have disease-specific meanings for systemic sclerosis and its CREST variant, respectively, the clinical significance of their concurrent existence has not been clarified. We investigated this condition in our case and with reference to the literature. For this purpose published reports between 1980 and 1998, where both ACA and ATA were measured simultaneously, were analysed by a MEDLINE search. In 10 papers 24 patients had both antibodies. In a further 25 reports, covering 3509 subjects who had either ACA or ATA, no concurrent existence was found. Prevalences of ACA (P(ACA)) and ATA (P(ATA)) in exclusive cases varied from 8.8% to 54.5%, and from 11.8% to 87.5%, respectively, whereas P(ACA) varied from 20.0% to 56.6%, and P(ATA) from 16.8% to 63.7% in the reports with patients positive for both. The actual prevalence of simultaneous presence was between 0.7% and 5.6%, significantly lower than the expected probabilities if both antibodies were to occur independently (p<0.005). In concurrently positive cases visceral involvement was characteristic, especially affecting the vascular system, with deterioration of oesophageal function and cutaneous lesions. We suggest that ATA and ACA do not coexist by chance, and that clinical characteristics with coexistence have a significance for the classification of scleroderma.