After a first episode of deep vein thrombosis (DVT), 30-50% of the patients will develop complaints suspect of recurrent DVT. Of these patients, only 20-30% do indeed have a recurrent episode of DVT. To identify patients with a true recurrent DVT, objective testing is mandatory in every patients. However, all the available tests have their limitations in patients with recurrent DVT. In this review, diagnostic strategies using venography, impedance plethysmography, 125I-fibrinogen leg scanning and ultrasonography in patients with recurrent DVT will be discussed. Furthermore, some epidemiologic data and pathophysiologic mechanisms concerning DVT will be considered.