cDNA sequencing of the first domains of DRB1, DRB3, DQA1, and DQB1 alleles was used to examine the extent of diversity in American black individuals expressing several DRw11 haplotypes. In addition to previously described DRw11 alleles, DRB1*1102 and DRB1*1103, two new DRB1 alleles, DRB1*11012 and DRB1*11042, were identified which differ from previously described alleles at the nucleic acid but not at the protein level. Gene conversion-like events have likely generated the DRw11 microvariation resulting in the merging of DRw11 with the DRw13 allele family. The DRw11 alleles are associated with various DQ alleles: DQw1 (DQw5 and DQw6), DQw7, and a serologically undefined DQ allele. This undefined DQ molecule, comprised of a DQ alpha/beta combination encoded by a DQw7 alpha gene (DQA1*0301) and a DQw2 beta gene (DQB1*0201), was previously observed in some DR7 and DR9 haplotypes. DRw11 haplotype diversity is augmented by the association of one of the DRw11 alleles with the DRw52c allele in contrast to the more common DRw11, DRw52b association. The extensive diversity exhibited by the DRw11 and DRw13 family of haplotypes coupled with their high frequency in populations of African ancestry suggest that the DRw11/w13 allele family may be very old and/or that these haplotypes carry some selective advantage.