The major complication of hematopoetic stem cell transplantation (HSCT) is graft-versus-host disease (GVHD) or graft. HLA incompatibility increases the frequency of GVHD. On the other hand, the risk is still available despite full matched HLAs, which may he related with non-HLAs or minor antigens. One of these minor antigens, HA-1 alelic incompatibility has been shown to be associated with GVHD in HLA-identical sibling transplants. The HA-1 is an HLA-A*0201 restricted non-peptide, winch derives from the cleavage of a protein encoded at clu-omosome 19. There are two :tidies of HA-1 created by a polymorphism at position 504 that results in either Histidine (HA-1.H) or Arginine (HA-1R). The aim a of the study is investigate the relationship between HA-1 and GVHD. We retrospectively examined the HA-1 locus in patients diaDiosed and treated between 1998-2004. We used PLR-SSP for typing HA-1. Forty samples from 20 HLA-A2 positive.HSCT ((BMT, n=3; PBSCT, n=17) recipients and their donors were included in our study. The frequencies of the three possible genotypes RR, RH, HH were 35%, 45% and 20%, respectively, in recipients and 35%, 65% and 0% in donors. Four of the 20 patients (20%) were determined as having evre II or III GVHD. There is HA-1H incompatibility between donor and recipient only in two patients with GVHD. mHAgs were found to be incompatible in 8 out of 20 recipient/donor pairs