There is a close correspondence between serologically defined DR types and DR beta chain restriction fragment length polymorphisms (RFLPs). There is also an association between DR types and DQ alpha and DQ beta RFLPs because of linkage disequilibrium. We present the results of an analysis of DR beta, DQ alpha and DQ beta RFLPs in Asian Indians and white Caucasian subjects. DR beta RFLPs were similar in the two groups. Clearly distinguishable DR beta patterns were observed for DR1, 2, 3, 4, 5, 7 and w10. The DR beta patterns associated with DR3 were, however, also found with w6. The DR7 DR beta patterns were also found with w9. For DR specificities 1, 3, 4, 5, 7 and w10, the associated DQ alpha and DQ beta RFLPs were similar in both racial groups, but for DR2, however, marked differences were found. The DR2-positive white Caucasian subjects all possessed a single DQ alpha/DQ beta combination whereas the DQ alpha/DQ beta patterns in DR2-positive Asian Indians showed considerable heterogeneity. The pattern seen in white subjects was present in only a minority of Asians. DR-DQ relationships clearly vary in different racial groups. RFLP analysis of HLA-linked diseases in different populations should prove to be an important technique in identifying the primary genetic factor(s) in these disorders.