Preliminary analysis of HLA class I typing of 618 individuals (patients and healthy members of 153 families) referred to the National Polish Bone Marrow Donors Registry (NPBMDR) for a donor search revealed that the number of undetected locus A and B antigens was more frequent than it was reported in a large scale population study in Poland (0.28 vs 0.076, p=0.000). This was associated with a lack of typing of family members for 51 out of 153 patients. 171 individuals primary typed (140 by serology and 31 by DNA typing) in 6 different Polish institutions were retyped in our laboratory with the use of PCR-SSO or PCR-SSP techniques. The results were discrepant in 50 cases (29%) including 19 patients and 31 family members. In 46% one DR specificity was missing, false typing of one or two specificities was evident in 46% and 14% of erroneous typing, respectively. The highest rate of errors was found in DRw52 group of specificities with the most difficult DR13 (32% of all false typing and 67% of errors within DRw52 group).