In patients with haemophilia, a close correlation is usually observed between the clinical expression of the disease and plasmatic factor VIII/factor IX clotting activity. However, some patients experience milder bleeding phenotypes than others, although they exhibit a similar biological profile. The high prevalence of some inherited thrombophilia risk factors offers the possibility of a co-inheritance in haemophilic patients which could influence the phenotypic expression of the disease. Rare thrombotic complications occurring in haemophiliacs could also be facilitated by the co-inheritance of modifier genes. The majority of thrombotic events occurring in haemophiliacs are in relation to clotting factor infusions or central venous catheters. Concerning surgical situations, in the absence of therapeutic recommendations, postoperative thromboprophylaxis is not systematically performed in haemophiliacs. However, substitutive treatment more or less completely corrects the coagulation defect and makes the venous thrombosis risk closer to the control population. It should be emphasized that haemophilia does not fully protect against venous thromboembolic disease. Patients with haemophilia very infrequently experience thrombotic events. Thus, the management of thrombotic complications occurring in haemophilic patients should be discussed in each case according to the precipitating risk factors, the clinical context and the thrombo-haemorrhagic balance of the patient with respect to a particular clinical situation.