The CTLA4 molecule is a homolog for CD28, and both molecules and their common ligands (CD80 and CD86) constitute the B7/CD28-CTLA4 co-stimulatory pathway for T cells activation. The CTLA4-ligand interaction has an inhibitory effect on T cell activation and might contribute to peripheral tolerance. A recently described CT60 A/G polymorphism affects the production of soluble CTLA4 and is strongly associated with immune-mediated diseases and with allogenic stem cell transplantation outcome. Thus, we examined this marker on liver transplant outcome by a PCR-RFLP method. The CT60 G allele was significantly associated with acute rejection (Pc=0.038; OR=1.49; AR vs. NAR). Patients who lacked this allele had the lowest risk of acute rejection development. Allograft survival data did not show statistical differences between genotypes. In conclusion, CT60 A/G dimorphism within the 3'-UTR of CTLA4 gene, which encodes for reduced sCTLA4 production, influence acute rejection development in liver transplantation.