SUMMARYAutoantibody reaclivily to cenlromere prolcins CENP-A. CENP-B and CENP-C was examined in 58 patienls with systemic sclerosis (SSc). 218 first degree relatives and 22 spouses, HLA class II typing for HLA-DRBI and HLA-DQAI was performed by reslriction fragment lenglh polymorphism (RFLP) analysis in 50 families, and HLA-DRBI, HLA-DQAI and HLA-DQBl typing was performed by olignueleolitlc typing in 44 families. Eleven probands and two relatives had ACA. The two relatives with ACA also had SSc. One relative was an identical twin sister of a proband with ACA and Iheother relative was a sister of a proband with ACA. All ACA-positivc probands and relatives were female, and all recognized CENP-A. CENP-B and CENP-C. The presence of at least one HLADQBl allele not coding for leueine at position 26 of the first domain appeared nceessary. although not sufficient for the generation of ACA, Therefore within SSc families ACA is strongly associated with female gender and disease phenolype, and is at least in part genetically determined.