Summary. Background: In recent years there has been a significant increase in the diagnosis of sudden sensorineural hearing loss (SSHL) in western, countries with an incidence of 20 of 100 000 people affected every year. No clear causes for this disease have been found thus far, but cochlear ischemia has been hypothesized in patients in whom an infectious episode or acoustic neurinoma have been excluded. Objectives: The aim of this case–control study was to investigate a number of acquired and inherited thrombophilic risk factors [antithrombin, protein C and S; factor V (FV) Leiden, FII polymorphism; lupus anticoagulant (LA); anticardiolipin (aCL) antibodies; fasting homocysteine (Hcy); lipoprotein(a) (Lp(a)); plasminogen activator inhibitor-1 (PAI-1)] in addition to cardiovascular risk factors in patients with idiopathic SSHL (ISSHL). Patients and methods: We investigated 155 patients (67 male/88 female; age: 55 (range 19–79 years) with a diagnosis of ISSHL within 30 days from the onset of symptoms, and 155 controls (67 male/88 female; age 54 (range 19–78 years). Fasting Hcy levels were significantly higher in patients than in controls [11.6 (6.7–60) μmol/L vs. 8.7 (5.0–24) μmol/L] as well as PAI-1 levels [19 (2–95) mg/dL vs. 14.5 (4.0–87) mg/dL]. Lupus anticoagulant was present in 13 of 155 (8.4%) patients; 20 patients (12.9%) had positivity of aCL (four IgM and 16 IgG). In no patient was a deficiency of physiological clotting inhibitors antithrombin, protein C and protein S found. No significant differences between patients and controls were observed for Lp(a) plasma levels [111 (1–1146) mg/L vs. 103 (11–695) mg/L] and for the presence of FV Leiden (4.5% vs. 4.5%) and FII variant G20210A (3.8% vs. 3.2%). Results and conclusions: Independent risk factors for ISSHL at the multivariate analysis (adjusted for age, sex and the traditional cardiovascular risk factors) were the positivity of aCL: OR 5.6 (95% CI 2.0–15.3); cholesterol levels within the second and third tertiles (with respect to the first tertile): T2 = OR 4.8 (95% CI 1.9–12.6)/T3 = OR 19 (95% CI 7–50.1); PAI-1 and Hcy levels within the third tertile (with respect to the first tertile): OR 20 (95% CI 7.8–78) and OR 4.0 (95% CI 2.0–8.1), respectively. These preliminary data suggest that hypercholesterolemia, hyperhomocysteinemia, elevated PAI-1 levels and anticardiolipin antibodies are associated with ISSHL, so indirectly supporting the hypothesis of a vascular occlusion in the pathogenesis of the disease.