Cytotoxic T-lymphocyte antigen-4 +49G/A polymorphism is associated with increased risk of osteosarcoma. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a potent immunoregulatory molecule that suppresses anti-tumor response by down-regulating T-cell activation. CTLA-4 gene +49G/A polymorphism (rs231775) has been reported to be associated with various cancers. Objective: The objective of this study is to investigate the association between CTLA-4 gene +49G/A polymorphism and the susceptibility to osteosarcoma in the Chinese population.The CTLA-4 variant +49G/A was detected by polymerase chain reaction-restriction fragment length polymorphism in 205 osteosarcoma cases and 216 age-matched healthy controls. Data were analyzed using the Chi-square test.Frequencies of the CTLA-4 +49AA genotype and the +49A allele were significantly increased in patients with osteosarcoma compared to healthy controls (OR 2.27, p=0.010, and OR 1.41, p=0.015).Our data suggest that the +49G/A polymorphism of CTLA-4 gene is associated with increased susceptibility to osteosarcoma.