This article will focus on the relationship between serum levels of anti-citrullinated peptide antibodies (anti-CCP) or rheumatoid factor (RF) and clinical response to TNF-alpha blockers in order to evaluate whether these antibodies may have a role as serological markers of response to therapy in rheumatoid arthritis (RA). The changes induced in anti-CCP levels after TNF blocking therapy still remain a controversial issue even though a marked reduction following conventional DMARDs has been reported in early disease. On the other hand, a drop in RF levels during treatment has been reported by many authors. Decreased IgM RF levels seem to parallel clinical response suggesting that this antibody can also be regarded as a marker of response to treatment. Pre-treatment RF positivity or negativity does not influence response to TNF-alpha blocking therapy while high pre-treatment levels of IgA RF seem to be associated with a poor response rate.