Thromboembolic complications during pregnancy are frequent in patients with congenital antithrombin III deficiency. We report on a 29-year-old patient with congenital antithrombin III deficiency and severe pulmonary embolism treated with recombinant tissue plasminogen activator. The diagnosis of antithrombin deficiency is retrospective. This case indicates that the risk of thrombolytic therapy in this clinical setting might have been overemphasized.