In all, 36 patients with progressive systemic sclerosis (29 women, 7 men) were studied clinically and immunologically; 15 patients had acrosclerosis (type I) and 21, sclerosis extending beyond the wrist (type II). The sera of all patients were evaluated for ANA (HEp-2-cells), Scl-70, centromere and other ENA antibodies. The centromere antigen was characterized by immunoblotting. All patients had high-titer ANA antibodies (100%); 36% of patients had the Scl-70 antibody (a marker antibody for PSS); and in 22% of our patients a centromere antibody was detected. In all cases the anti-centromere sera reacted with a 19.5-kd polypeptide and in 2 cases they reacted with 23- and 25.5-kd proteins in addition. In patients with centromere antibodies there was increased organ involvement (heart, lung, kidney) compared with patients who had anti-Scl-70 or other nuclear antibodies.