AbstractHLA in systemic scleroderma (PSS), including three familial cases, is reported. Three families in which one sister developed PSS and another sister suffered from either PSS (family 1), mixed connective tissue disease (MCTD) (family 2), or Sjögren's syndrome (SjS) (family 3) were described. The elder sister in family 1 died of respiratory insufficiency caused by scleroderma lung. The sisters in family 2 both had SjS, anti SS‐A antibodies, and HLA A2‐Bw55‐Cwl‐DRw8 haplotype in common. The elder sister with PSS in family 3 also had SjS and Hashimoto's thyroiditis. HLA in 28 PSS patients including these 3 familial cases were analyzed with 4 MCTD and 4 generalized morphea patients. HLA A2, Bw46, DR2, DRw8, DRw6 and DQw1 antigens were more frequently found in the PSS patients than in the controls. HLA DRw6 was the only antigen that was positive in common in the 3 familial cases. In those patients with anti topoisomerase I antibodies, HLA DR2 antigen was found more frequently than in the controls. Some, but not all, of these results were similar to the previous reports on HLA in PSS. Further investigations on more patients and the other members of these families would be necessary to clarify the significance of these