Frequency and diagnostic significance of two scleroderma-specific antinuclear antibodies were examined in 104 patients with progressive systemic scleroderma (PSS). Antibodies against an antigen in the centromere region of chromosomes (centromere antibodies) were demonstrated by indirect immuno-fluorescence on HEp-2 cells in 18 patients (17%) and antibodies against Scl-70 nucleoprotein (Scl-70 antibodies) by gel precipitation with soluble nuclear extracts (ENA) in 21 patients (20%). In none of the patients did both antibodies occur. In patients with Scl-70 antibodies severe illness was predominant with extensive cutaneous sclerosis in 86%, lung involvement in 85% and joint involvement in 89%. Humoral inflammatory signs were marked in this group. Patients with centromere antibodies predominantly had acroscleroderma (56%) with subcutaneous calcinosis (83%) and telangiectasias (83%), as known from the CREST syndrome. Humoral immune phenomena were rare. With regard to Raynaud's syndrome, involvement of the oesophagus, age and the duration of disease, there was no difference between the two groups. On the other hand, in patients with centromere antibodies lung involvement (22%) and joint involvement (35%) was significantly less common (P less than 0.01) than in all other scleroderma patients. Centromere antibodies and Scl-70 antibodies, which can be demonstrated already in the symptom-poor early phase of PSS, can thus be used as diagnostic parameters for different forms of PSS with differences in the degree of skin and organ involvement.