Etanercept and infliximab treatments are often associated with autoantibodies induction. Their reported prevalences vary among different studies and the conclusions are somehow conflicting, mainly regarding whether the two drugs induce the same modifications. In this small prospective study, specifically designed to identify transient phenomena, we assess the prevalence of different relevant rheumatologic autoantibodies during anti-TNF-alpha courses in patients with rheumatoid arthritis. We report that both etanercept and infliximab transiently induce anti-DNA antibodies in 50-78% of patients, respectively, and these antibodies seem to be different from the typical lupus associated ones. Antinuclear antibodies (ANA) increased their titres and were newly produced up to 100% of patients. No other relevant antibodies are affected. Finally, as also confirmed for the first time by the patients switched from one drug to the other, the two TNF-alpha blockers behave similarly.