This case report describes two 28-year-old healthy males, who werw admitted to hospital due to pain in the lower extremities. Both patients were diagnosed with deep venous thrombosis. In order to determine extent and treatment of the thrombosis, a CT angiography was performed in both patients showing infrarenal vena cava inferior agenesia. Investigation for causes of the thrombosis ruled out cancer and thrombophilia. The patients made full recovery with anticoagulant therapy and compression stockings. Permanent treatment with anticoagulants should be considered in patients with vena cava inferior agenesia.