Introduction: Cytotoxic T-cell lymphocyte antigen 4 (CTLA-4) is a member of the superfamily of immunoglobulins that are mainly expressed by activated T cells. It is established that blockade of CTLA-4 receptors leads to the enhancement of an immune response. Different polymorphisms of the CTLA-4 gene have been described which cause increased susceptibility to various malignancies such as lymphoma or multiple myeloma. Considering that bladder cancer is one of the most prevalent cancers worldwide, we have evaluated the role of CTLA-4 gene polymorphism at position +49 A/G in the formation or progression of bladder cancer in southern Iran.Materials and Methods:Atotal of 226 individuals between February 2005 and June 2006 were included and placed into two subgroups: patients diagnosed with bladder cancer and a control group. Demographic data and risk factors were collected from both groups. The DNAof all subjects was extracted from their blood samples. Different genotypes of the CTLA-4 gene were determined using the restriction fragment length polymorphism (RFLP) technique and data were compared in both groups by using Pearson's chi-square test.Results: The prevalence of AA, AG and GG genotypes at position 49, according to the PCR-RFLP method, were 57.5%, 37.2% and 5.3% in the control group, respectively. In the patient group, the prevalence of these genotypes was: AAin 57.5%, AG in 32.7% and GG in 9.8%. Statistical analysis of data showed no significant difference in both groups (P value=0.40). Also there was no correlation between different genotypes of the CTLA-4 gene and invasiveness of the disease in our cases.Conclusion: Although polymorphism of the CTLA-4 gene at position 49 of exon-1 increases susceptibility to several malignancies, our study showed no relationship between polymorphism at this position and genetic susceptibility to the development of bladder cancer, nor was there any association with disease progression.