Abstract:It has been shown that Greek RA patients do not show an increased frequency of HLA‐DR4 compared with Greek controls. As only the Dw4 and Dwl4 subtypes of DR4 are implicated in RA, we have characterised DR4‐positive Greek RA patients and controls using serology, MLC typing and RFLP analysis to see whether the distribution of. DR4 subtypes or other HLA antigens associated with DR4 could account for these findings. In the 10 patients and 12 controls studied, Dw10 was common, being present in almost half the controls. Dw4 was not detected in the controls, but was present in three of the RA patients, indicating that there may be some relationship between Dw4 and RA in this population; Dw13 and Dw14 were also found, Dw15 was not detected. Eight of the subjects did not type as any of the HLA‐D antigens mentioned. Three controls had unusual DR4‐DQ associations, two having DR4‐DQw2 and one possessing DR4‐DQw4. Analysis of the TaqI DRB RFLP of the subjects showed that one control did not have the 6.1 kb band characteristic of DR4s. All these results indicate that DR4 is a heterogeneous antigen in this population and that several as yet undescribed variants of DR4 may