AbstractThe CTLA‐4 molecule plays an important role in immune regulation by downregulating activation of T cells. Polymorphisms in the CTLA‐4 gene have been shown to be associated to a number of autoimmune diseases including blood disorders. In this study, the intragenic polymorphisms of the CTLA‐4 gene at position −318*C/T, +49*A/G, and the dinucleotide (AT)n repeat polymorphism in exon 3 were analyzed in patients with non‐Hodgkin's lymphoma. Genotype and haplotype analysis showed that the exon 1+49*AA genotype was over‐represented among patients with NHL (P = 0.002), whereas no difference was observed for the −318*C/T promoter and the (AT)n polymorphisms (P > 0.05). The data obtained indicate that the CTLA‐4+49A/G polymorphism may have a role in genetic susceptibility to NHL. Am. J. Hematol. 76:14–18, 2004. © 2004 Wiley‐Liss, Inc.