DPB1 locus typing of the 155 cell 4AOHW panel was performed using a PCR-RFLP method. Ambiguity of allele assignment was resolved by amplification using sequence-specific primers. Of the 150 cells for which typings were achieved, three exhibited unusual restriction enzyme fragment patterns, suggesting the possibility of novel DPB1 alleles. Sequence analysis revealed one allele present in the currently reported 46, one novel allele (4AOHW/107) not present among the 46, and one from a non-human primate which is being investigated. Twenty-six (26) of the 34 10IHW cells have been studied previously by cDNA RFLP, and strong haplotypic associations have been demonstrated between DPA1 and DPB1 locus alleles. It is proposed that exploitation of intron polymorphisms marking haplotypes will be an integral part of future DPB 1 typing as a ‘first-pass’ stratification process to minimize the requirement for sequence-based methods to definitively assign DPB 1 alleles.