A novel design for a low‐temperature valve is presented. Designed to be used on fill‐line capillaries and flow lines in low‐temperature apparatus, the valve has nearly zero dead volume as well as a very small total volume. It employs no metallic bellows as in standard valve designs. Instead, a Kapton membrane is epoxied into a cylindrical form to provide a flexible diaphragm, which is activated by pressurized helium. The valve is simple to construct, having only one machining operation, and uses materials readily available. It has been tested in liquid helium to be leaktight aboveT&lgr;with a 1‐bar pressure differential across the capillary containing the valve.