Autoreactive cytotoxic T cells play a key role in the pathogenesis of aplastic anemia (AA) by myelosuppressive cytokines including interferon gamma, tumor necrosis factor alpha, and transforming growth factor beta. As an important cytokine that modulates the cell cycle, the involvement of transforming growth factor beta-1 (TGF-β1) in AA has been studied. The purpose of our study was to investigate the role of (TGF-β1/2509) gene polymorphisms in patients with acquired AA and to assess whether genotype was associated with higher or lower production and compare it with established control populations. Thirty-one patients with acquired aplastic anemia and 30 age- and sex-matched healthy controls were analyzed consecutively using PCR–restriction fragment length polymorphism (PCR-RFLP). TGF-β1 polymorphism C-509T was identified using PCR-RFLP. Significantly different distributions of the gene were demonstrated between the case and the control. The frequencies of −509CT and −509TT genotypes (74.2 versus 30 % and 16.2 versus 3.3 %, respectively) were significantly higher in cases than in controls (P < 0.001), while the frequency of the −509 CC genotype is higher in the control than in cases (66.7 versus 9.6 %, P < 0.001). Our data showed a genotypic profile associated with high TGF-β production in patients with bone marrow failure and suggest that the genetic regulation of inflammatory and T cell-mediated immunological pathways could be involved in the pathogenesis of bone marrow failure, reinforcing the view that AA are organ-specific autoimmune disorders.