The cause of myasthenia gravis (MG) is unknown, but it is widely believed to be an autoimmune disease occurring in genetically susceptible individuals. The human leukocyte antigen (HLA) region is considered to be the most important genetic region for MG susceptibility genes. To investigate the association between HLA-DRB1 and myasthenia gravis (MG) in a northern Han Chinese population, a polymerase chain reaction with sequence-specific oligonucleotide probe hybridization method was used to determine the HLA-DRB1 genotypes of 91 patients with MG and 171 healthy individuals. We found that the HLA-DRB1*09 allele was significantly more prevalent among patients with MG than among healthy controls, especially those who experienced early onset of the disease (<= 40 years), those who were seronegative for acetylcholine receptor antibody, and those with ocular MG. The prevalence of the HLA-DRB1*08 allele was significantly lower among patients with MG than among controls. These results indicate that HLA-DRB1*09 might be positively associated and DRB1*08 negatively associated with MG in the northern Han Chinese population. (C) 2011 Published by Elsevier Ltd.