A case of a 21-year-old male with blunt abdominal trauma and subsequent acute thrombosis of the inferior vena cava, presenting as abdominal pain, is reported. The apparent mechanism of proximal inferior vena cava thrombosis with distal extension into the iliac veins differs from that suggested in earlier reports. Resolution of symptoms was achieved by heparinization and bedrest alone, in spite of thrombus in the suprarenal vena cava.