Patients with familial and non‐familial (sporadic) forms of rheumatoid arthritis (RA) were studied to investigate possible HLA heterogeneity. HLA‐DR4 was present in 75% of familial and 59% of sporadic RA patients. The frequency distribution of A2, B8, B27, Cw3 and DR3 differed somewhat between the two groups; however, the differences were not statistically significant in this small group of patients. Studies of a larger number of patients are indicated to explore the possibility of genetic subgroups in