Transcriptional regulation of inducible nitric oxide synthase (iNOS) is critically involved in the pathogenesis and progression of rheumatoid arthritis (RA); however, the specific transcription factors that control this process remain largely unidentified. In the present study, it was discovered that expression of the key erythroid factor, globin transcription factor 1 (GATA1), is significantly greater in human RA synovial tissues than in osteoarthritis (OA) tissues. IL 6 was found to induce synovial GATA1 expression in a signal transducer and activator of transcription 3-dependent manner. Functionally, knockdown of GATA1 expression using specific small interfering RNA treatment was found to compromise immunoreaction-elicited expression of proinflammatory cytokines and thus impair invasiveness of the human fibroblast-like synovial cell line MH7A, whereas introduction of exogenous GATA1 was found to promote production of proinflammatory cytokines, leading to greater aggressiveness of MH7A cells. Mechanistically, GATA1 acts as the transcriptional coactivator of NOS2 (the gene encoding iNOS) transcription. Collectively, these data suggest that synovial GATA1 is an essential contributor to development and exacerbation of RA, presumably by inducing NOS2 transcription.