The present paper demonstrates the usefulness of the temperature gradient gel electrophoresis (TGGE) as a precise method for the rapid identification of HLA-DR full matched donors by molecular crossmatch analysis. The resulting TGGE fingerprints are highly diverse for different HLA-DR genotypes and identical for samples with identical HLA-DR type, as shown for a panel of 25 randomly selected PCR-SSO pretyped DNA samples. In addition, TGGE analysis of a panel of homozygous typing cell lines (HTCs) established, that even subtle differences in the DR4 subtypes are detectable by TGGE crossmatch analysis. Furthermore, TGGE crossmatch analysis of unrelated donor/patient pairs demonstrated, that only HLA-DR identical patient/donor combinations showed identical TGGE patterns. Thus crossmatch analysis by TGGE presents a novel basis for a rapid and safe unrelated bone marrow donor selection strategy. Only HLA class I identical donors which also show HLA-DR identity in the TGGE crossmatch test are selected for the final confirmation of the HLA class II genes by a suitable DNA subtyping method.