Despite recent intensive media interest, the incidence of traveler's thrombosis is unknown. We have undertaken a study of all symptomatic cases of venous thrombosis, presenting to a hospital, in a fixed population of 650,000. There were 1,250 cases of venous thromboembolism diagnosed over a 2-yr period. Of these, only 47 (3.8%) answered positively to the question" did you make a journey of more than 100 mi in the 4 wk prior to diagnosis?" Among the travelers, 60% had traveled by air, 36% by road, and the remainder by rail. At least one medical risk factor for venous thrombosis was present in all but three of our cohort. We conclude that, taking into consideration the enormous number of passengers who travel, the relative risk of traveler's thrombosis is likely to be low. The incidence of this complication in the North East of England is 1 per 27,660 of the whole population.