ESPOIR (Etude et Suivi des POlyarthrites Indifférenciées Récentes) is a multicentre national cohort sponsored by the French Society for Rheumatology. The patients had early arthritis (<6-month disease duration), had a certain/probable clinical diagnosis of RA or undifferentiated arthritis potentially becoming RA and were DMARDs or glucocorticoids naïve. ESPOIR is a cohort of early arthritis, highly enriched for rheumatoid arthritis (RA) patients, since in patients followed for 5 years more than 90% met ACR/EULAR criteria for RA. A total of 813 patients were enrolled between December 2002 and March 2005 in 14 academic regional centres with the participation of a network of private rheumatologists. Today, 104 clinical research projects have been selected by the scientific committee of the cohort. The projects focus on data from the first 5 years of follow-up. Many studies are in progress, and 54 original articles have been published. The research projects cover a wide range of topics, including environmental factors, diagnosis, evolution, and prognosis, evaluation of disease, imaging, genetics, biomarkers, medical economics and therapeutic strategies.