Cytokine pathways are central to the perpetuation of synovial inflammation in rheumatoid arthritis (RA). Azathioprine (AZA) has disease modifying activity in RA. This study addressed the effect of AZA on serum IL-6 and soluble IL-2 receptor (sIL-2R) levels in RA. Over a 24 week period of therapy significant clinical improvement was observed. However, serum levels of both IL-6 and soluble IL-2R levels did not significantly change after AZA therapy. AZA therapy did not significantly alter the peripheral blood monocytes ability to produce IL-6 in vitro, either in the presence or absence of LPS. The mechanism by which AZA achieves clinical improvement in RA patients does not appear to be through IL-6 modulation or modification of synovial lymphocyte activation as assessed by serum sIL-2R levels.