Central retinal vein occlusion (CRVO) is a complex trait caused by a number of local and systemic factors. Among the latter, atherosclerosis has been attributed a major pathogenic role. Recently, the paraoxonase/arylesterase (PONA) enzyme has been implicated in the pathogenesis of atherosclerosis. There is a 10- to 40-fold variability in the activity of this enzyme among individuals. This variability is due to the presence of an A/G polymorphism in the coding region of the gene. The A and G alleles code for glutamine (A genotype) and arginine (B genotype), respectively. We determined the PONA genotypes and alleles in 42 patients with CRVO and in 45 control subjects of the Japanese population. The distribution of AA, AB and BB genotypes were 9.6, 45.2 and 45.2%, respectively, in the patients and 26.7, 53.3 and 20.0% in the control subjects, respectively (p < 0.05). The A allele frequency was 0.32 in patients and 0.53 in controls (p < 0.01). In conclusion, molecular variants of the PONA gene are involved in the predisposition to CRVO. Further studies are needed to characterize the molecular mechanism by which the PONA enzyme is involved in atherosclerosis.