Background: To estimate the incidence and associated risk indicators of deep venous thrombosis(DVT) in the lower extremities. Patients and methods: A population-based 5-year follow-up study with self-administered questionnaire. The study included 5568 persons at the beginning, with a follow-up of 17005 person-years. A questionnaire was sent to all residents in the city of Tampere, Finland, born in 1929, 1939 and 1949. In the first survey the number of participants was 5568 and in the second questionnaire 4903. The participation rates were 83% and 88%. Results: The incidence of DVT was 140 per 100 000 person-years. The life-time prevalence of DVT was 3.1%. In a univariate analysis, the appearance of a new DVT during the follow-up time (incidence) was statistically significantly associated with pre-existing varicose veins, sex-steroid therapy, heart failure and arterial insufficiency in the lower limbs. rn multivariate analysis varicose veins, arterial insufficiency in the lower limbs and sex-steroid therapy remained as significant risk factors associated with DVT Conclusions: The study confirms that the incidence of DVT in Finland is dose to the estimates in other Western populations. Pre-existing varicose veins, sex-steroid therapy and arterial insufficiency in the lower limbs are independent risk factors for DVT in our population-based study.