Aims were to determine the prevalence of the HLA-B27 phenotype in a group of patients with RA, and to evaluate the clinical, radiological and, serological characteristics of RA in relation to this phenotype. All relevant information was obtained retrospectively from the standardized clinical records of 311 RA in-patients first admitted to the Rheumatology Unit of the Brest University Medical School. In the control population of Britanny, the frequency of HLA-B27 has been shown to be 12%, while HLA-B27 was present in 30 (9.6%) of the 311 RA patients. There was no significant association between demographic, clinical, biological, or radiological characteristics of the patients on the one hand, and the presence of the HLA-B27 allele on the other. The subgroup of RA patients with HLA-B27 had however a slightly higher IgA level than that without HLA-B27. Ankylosing spondylitis were found to coexist in three patients who all were HLA-B27 positive. We conclude (1) that the prevalence of HLA-B27 is not higher in French RA patients than in the normal controls, and (2) that HLA-B27 typing is not useful in RA. HLA-B27 does not confirm nor does it reject the diagnosis of associated ankylosing spondylitis.