Guillain-Barré syndrome in northern China occurs in two forms: acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN). AMAN and AIDP have an immunologic basis, and some cases are associated with preceding Campylobacter jejuni infection. The distribution of allelic forms of the histocompatibility genes HLA-DPB1, DQB1, DRB1, DRB3, DRB4, and DRB5 was examined by DNA-based technology in 34 control, 12 AIDP, and 31 AMAN cases. In AIDP patients, the DRB1*1301 allele showed a significant increase (18% vs. 0%, P = .055). In AMAN patients, alleles DRB1*1301-03 and DRB1*1312, taken collectively, were increased (19% vs. 0%, P = .009), but by itself, the DRB1*1301 allele was not increased, as in AIDP patients. With a larger number of persons, more definitive statements will be possible; however, the differential distribution of DR13 allelic forms between AIDP and AMAN cases may suggest that there are different immunologic mechanisms operating at the molecular level of these diseases.