The association of MS with the HLA class II loci DR and DQ was investigated in subjects of Shanghai Chinese and British Caucasian origin. Our aim was to determine whether common alleles predispose to the disease in both races. In the Caucasian population MS was significantly positively associated with the putative haplotype DRB1*1501, DQA1*0102, DQB1*0602. In contrast, HLA class II alleles were not found to predispose to the disease in the Shanghai Chinese, suggesting that this haplotype is unlikely to be a universal susceptibility determinant. The absence of a disease association with the HLA-DR and -DQ genes in the Chinese population has a number of possible explanations. Our study suggests that other genetic and/or environmental components may be more important in determining susceptibility to MS in this race.