The purpose of this paper is to document the development of ASME Section X Code rules for high pressure vessels for containing hydrogen and to provide a technical basis of their content. The Boiler and Pressure Vessel Project Team on Hydrogen Tanks was formed in 2004 to develop Code rules to address the various needs that had been identified for the design and construction of up to 15,000 psi hydrogen storage vessel. One of these needs was the development of Code rules for high pressure composite vessels with nonload sharing liners for stationary applications. In 2009, ASME approved new Appendix 8, for Section X Code which contains the rules for these vessels. These vessels are designated as Class III vessels with design pressure ranging from 21 MPa (3000 psi) to 105 MPa (15,000 psi) and maximum allowable outside liner diameter of 2.54 m (100 in.). The maximum design life of these vessels is limited to 20 years. Design, fabrication, and examination requirements have been specified, including Acoustic Emission testing at the time of manufacture. The Code rules include the design qualification testing of prototype vessels. Qualification includes proof, expansion, burst, cyclic fatigue, creep, flaw, permeability, torque, penetration, and environmental testing.