Background: Metastasis associated gene-1 (MTA1), was initially discovered in aggressive human cancer cell lines and has been subsequently associated with the invasiveness and metastatic potential of cancer cells. Materials and Methods: In the present study, we evaluated the expression levels of MTA1 in a cohort of human pituitary tumors (n=95) and examined the relationship between MTA1 expression and the pathological, clinical and aggressiveness of these tumors. Results: MTA1 was expressed at significantly higher levels in large tumors and in those with higher tumor grade. It was also observed that tumors that had invaded the suprasellar bones and tumors that destructed the sella had significantly higher levels than those without bone involvement (p<005). Although there did not appear to exist any relationship between MTA1 and cystic lesions in the tumors, endocrine-active tumors, namely those secreting prolactin, growth hormone, Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) had significantly lower MTA1 transcript levels than inactive tumors. Conclusion: MTA1 is associated with the aggressive nature of pituitary tumors and may be a potential therapeutic target in this tumor type.