Several reports have suggested a possible relationship between blood coagulation factors and schizophrenia. Plasminogen activator inhibitor type 1 (PAI-1) belongs to a serine protease inhibitor family, which regulates fibrinolysis and proteolysis by inhibiting plasminogen activation. The purpose of this study was to investigate the association of polymorphisms of the PAI-1 gene with schizophrenia in Korean population. Two important polymorphisms (-675 4G/5G and -844 G/A) located on promoter region of the PAI-1 gene were analyzed on 178 schizophrenia patients and 226 controls. The genotypic and allelic associations of -675 4G/5G were found significant. Furthermore, haplotype analysis revealed significant result, which suggests that -675 4G/5G polymorphism might confer increased susceptibility for schizophrenia in Korean population.