Abstract: A detachable balloon catheter apparatus and method. The apparatus includes an introducer catheter which is attached at its trailing end to a source of pressurized fluid. The leading end of the catheter is attached to an inflatable balloon which may be inflated as the pressurized fluid is injected through the introducer catheter. A valve mechanism is positioned inside the assembled introducer catheter and balloon and the leading end of the valve mechanism is bonded to the interior of the balloon. As the balloon is inflated by the pressurized fluid, a forwardly directed lateral force is exerted on the valve mechanism so that it is pulled forward into fluid-tight engagement with the valve seat placed at the opening of the balloon. Once the valve mechanism is pulled into fluid-tight engagement so as to close off the opening of the balloon, further injection of the pressurized fluid serves to detach the inflated balloon from the introducer catheter.