Primary or acquired hypercoagulable states favour thrombotic events. The identification of prothrombotic states is of immediate practical usefulness in the orientation, prophylaxis and treatment of pulmonary embolism. Detection of individuals resistant to activated protein C. the most frequent laboratory anomaly in the study of patients with venous thromboembolism, offers a better approach for these patients as well as a better prophylaxis and orientation of their direct relatives concerning thromboembolic events. The authors describe the clinical case of a young woman, previously healthy, who developed serious pulmonary thromboembolism, the resolution of which was difficult and the evolution unusual. Later, a state of resistance to activated protein C (aPCr) was identified. Concerning the case described, the authors reflect on hypercoagulable situations, especially "aPCr" states.