A new silicone detachable balloon has two self-sealing valves. The proximal valve grips the catheter tip, and the distal valve allows a guide wire to pass through. The balloon is advanced over the guide wire. Detachment is performed after the wire is withdrawn. Five balloons were successfully placed in the intended arteries and veins of three dogs. This wire-directed detachable balloon is placed more easily and accurately than the conventional detachable balloons that are placed with the flow-directed method.