Rheumatoid arthritis (RA) is a chronic systemic disease that leads to increases in health system economic burden through direct and indirect costs, including chronic treatment, reduced productivity and premature mortality. Anti-TNF agents have represented a major advance in the treatment of RA. The most commonly used (adalimumab, etanercept and infliximab) have demonstrated their cost-effectiveness at label doses. However, physicians may need to adapt the treatment by increasing the dose when a drug is not effective enough or by reducing it when there is a sustained effectiveness. In a cross-sectional study conducted in our hospital in which information from RA patients treated with anti-TNF drugs under conventional and modified doses were collected, the authors analyzed the costs of the medication in order to estimate the mean patient-year cost, the annual costs related to clinical efficacy and the cost per responder patient to anti-TNF treatment when dosage modification is undertaken in daily clinical practice.