Venous thromboembolism (VTE) causes considerable morbidity and mortality. About half of all VTE cases in adults are related to recent hospitalization, in spite of the clinical guidelines regarding prophylaxis. We aimed to assess the frequency and the independent risk factors in VTE in hospitalized patients, and to compare the risk factors in medical versus surgical cases. A case-control study consisting of 732 patients (382 with VTE and 350 controls) was designed. At least one risk factor was found in 90.31% of VTE cases; more than half of the patients presented multiple risk factors, associated with a double risk comparatively to the intervention of only one factor. A similar distribution of the risk factors was found in both medical and surgical patients, except for congestive cardiac failure (predominant in medical cases) and respectively, varicose veins, previous episode of VTE and cancer (predominant in surgical VTE patients). The independent risk factors in VTE were the following: previous episode of VTE, obesity, chronic obstructive pulmonary disease, congestive cardiac failure, varicose veins and cancer. The study shows the importance of the risk factors in VTE and the need to detect hospitalized patients at risk in both medical and surgical cases.