HLA antigen distribution was studied in 126 patients with systemic sclerosis (SSc) followed prospectively and compared to that of 325 healthy controls. The frequencies of HLA antigens DR3, DR5 and DRw52 were increased in patients with diffuse skin involvement (P = 0.02, 0.05, 0.03). The presence of DRw52 (relative risk [RR] much much greater than 1) and DRw6 (RR = 54.5) was associated with significantly increased risks of a fatal disease outcome with pulmonary hypertension (PHT). In the absence of PHT, DRw252 was inversely associated with the risk of death. These findings indicate an adverse prognosis in SSc when PHT is present in association with DRw52.