Impaired cochlear blood circulation has been suggested to cause sudden hearing loss. In this study, the role of factor V 1691 G-A (FV 1691 G-A), prothrombin 20210 G-A (PT 20210 G-A), methylene tetrahydrofolate reductase 677 C-T (MTHFR 677 C-T), factor V 4070 A-G (FV 4070 A-G), endothelial cell protein C receptor (EPCR) gene 23-bp insertion, and plasminogen activator inhibitor-1 (PAl-1) 4G/5 G mutation was assessed. Fifty-three patients with idiopathic sudden sensorineural hearing loss and 80 individuals comprising the control group were included in this study. The frequency for FV 1691 A was 6.2% in the patient group and 3.7% in the control group, PT 20210 G-A was 1.2% in the patient group and 1.9% in the control group, and FV 4070 A-G was 7.5% in the patient group and 11.3% in the control group. The frequency of MTHFR 677 C-T was significantly higher in the patient group than in the control group, with a P value of .03. PAI-1-675 4G/5G polymorphism was found to be 71.2% and 69.8%, in the control group and the patient group, respectively. The EPCR 23-bp insertion was 0% in the control group and was found in 3 patients (3.7%), which needs further study.