A 27-year-old woman, after 31 weeks of amenorrhoea during her second pregnancy, developed a left external iliac and femoral deep vein thrombosis, confirmed by venous ultrasonography and magnetic resonance imaging. The infusion of tissue plasminogen activator (rt-PA: 1.2 mg/kg, i.e. 80 mg over 3 hours), on the 2nd day, allowed revascularization of the femoral junction, while the external iliac vein remained occluded. The patient did not develop pulmonary embolism or haemorrhage, particularly obstetric haemorrhage. The subsequent pregnancy was uneventful until delivery, six weeks later, of a normal child. Three years later, the patient has no sequelae of her deep vein thrombosis. When required by the patient's condition, it seems that rt-PA can be used to treat severe deep vein thrombosis during pregnancy, either isolated or complicated by pulmonary embolism. Very rigorous cardiological, obstetric and laboratory surveillance is essential. A sufficient dosage, identical to that used in clinical settings other than pregnancy and a brief treatment duration (2 to 3 hours) are probably more effective and more reliable than lower doses continued for several days. However, the risk of haemorrhage remains difficult to predict and its prognosis, especially foetal, is often very poor. A larger series of cases is therefore necessary before this drug can unreservedly recommended in pregnant women.