OBJECTIVE: While there is consensus that treatment with disease-modifying antirheumatic drugs (DMARDs) should be started early in patients with inflammatory arthritis, confirmation that radiographic progression is inhibited with early treatment start is scarce. This study was undertaken to compare radiographic progression in patients treated with a DMARD very early in the course of their disease (within 3 months of diagnosis) and those who began DMARD treatment later. METHODS: Patients included in the French observational ESPOIR (Étude et Suivi des Polyarthrites Indifférenciées Récentes [Study and Followup of Early Undifferentiated Polyarthritis]) cohort were followed up, and radiographic progression after 12 months was assessed. Propensity scores, reflecting the indication to start a DMARD, were obtained by modeling the start of DMARD therapy by disease-specific and demographic variables obtained at baseline, using logistic regression analysis. The influence of very early versus delayed DMARD start on radiographic progression was evaluated by generalized linear regression, with and without adjustment for propensity scores. RESULTS: Six hundred sixty-one patients were analyzed. In an unadjusted analysis, patients starting DMARD therapy within 3 months of diagnosis did not show a significant difference in radiographic progression score as compared to those starting DMARD therapy later (1.2 units versus 1.6 units; P = 0.37). Adjustment for the propensity score revealed a statistically significant difference in mean progression (0.8 units versus 1.7 units; P = 0.033). Analysis by propensity score quintile showed a trend suggesting that early treatment was especially beneficial for patients in the fourth and fifth quintiles (worse prognosis). CONCLUSION: Our findings indicate that among patients with inflammatory arthritis in daily clinical practice, early initiation of DMARD therapy reduces 12-month radiographic progression. This strengthens the current recommendations for very early initiation of specific therapy in patients with early arthritis.