Abstract: The invention provides highly adaptable valves for providing hemostasis about minimally invasive surgical implements such as guidewires and endovascular prosthetic delivery catheters. The valves generally comprise an elastomeric sealing body which will maintain hemostasis by contacting a surgical implement traversing the valve over a very small contact area. Preferably, the orifice is formed in a thin membrane which extends radially inward from a torroidal balloon having a relatively rigid outer rim and a flexible inner portion. When a vacuum is applied within such a balloon, the flexible inner portion pulls the membrane radially outward to expand the orifice diameter. A positive pressure can be applied within the torroidal balloon so that the balloon expands radially inward to block access through the valve.