Some acquired aplastic anemia (AA) results from immune-mediated destruction of hematopoietic stem cells. Cytokine gene polymorphisms are implicated in controlling cytokine production and increasing the susceptibility to some autoimmune diseases. We characterized the IL-6/-174, TNF-alpha/-308, IL-10/-1082, IFN-gamma/+874, TGFbeta1/-509 single nucleotide polymorphisms (SNP's) and the IL1-RA second intron variable number tandem repeat (VNTR) alleles in 73 patients with AA and compared the frequency of genotypes to established control populations. We found that some patients with acquired AA have polymorphisms which are linked to high production of proinflammatory cytokines, particularly TNF-alpha and IFN-gamma.