A variable hemostasis valve is disclosed that may be used during medical procedures to prevent blood loss while permitting the percutaneous introduction, operation, and removal of medical instruments. A flexible tubular seal element is disclosed that is disposed within the variable hemostasis valve to provide a fluid-tight, adjustable seal. After insertion of a medical instrument into the valve through at least a portion of the flexible tubular seal element, a proximal portion of the valve housing may be rotated to cause the tension of the flexible tubular seal element to increase over the inserted medical instrument and engage the valve in a closed position. The proximal portion of the valve housing may then be rotated in an opposite direction to release the seal and return the tubular seal element to a relaxed lumen open position.