PURPOSE To investigate whether the LOC387715 polymorphism is associated with polypoidal choroidal vasculopathy (PCV) and with vitreous hemorrhage (VH), one of the most severe clinical phenotypes, in the Japanese population. DESIGN Cross-sectional case-control association study. METHODS One hundred and nine Japanese patients with PCV, composed of nine patients associated with VH (VH group) and 100 patients without VH (non-VH group), and 85 control subjects were analyzed for the LOC387715 polymorphism (rs = 10490924), using denaturing high-performance chromatography. RESULTS There was a significant difference in the T allele frequency between PCV patients and control subjects (P < .0001). In comparison with wild-type homozygosity (GG), homozygosity for the at-risk allele genotype (TT) increased the likelihood for PCV 8.4-fold (3.6 to 19.5, 95% confidence interval [CI]) and heterozygosity for the at-risk allele genotype (TG) increased the likelihood for PCV 4.0-fold (1.9 to 8.4, 95% CI). There was a significant difference in the genotypic frequency at the LOC387715 site between the VH and non-VH groups (P = .0099, Chi-square test) with the TT genotype occurring in 88.9% in the VH group and 37.0% in the non-VH group. The frequency of the T allele in the VH group was significantly greater than that in the non-VH group (0.944 vs 0.610; P = .0039, Fisher exact test). CONCLUSIONS The LOC387715 polymorphism is associated with PCV and clinical severity in the subgroups of PCV in the Japanese population.