The capabilities in the Hydrogen Effects on Materials Laboratory (HEML) at Sandia National Laboratories and the related materials testing activities that support standards development and technology deployment are reviewed. The specialized systems in the HEML allow testing of structural materials under in-service conditions, such as hydrogen gas pressures up to 138 MPa, temperatures from ambient to 203 K, and cyclic mechanical loading. Examples of materials testing under hydrogen gas exposure featured in the HEML include stainless steels for fuel cell vehicle balance of plant components and Cr-Mo steels for stationary seamless pressure vessels. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.