Fatigue lifetime of model AF1410 ultrahigb-strength steel as a function of fatigue hold time (time expended at peak loads) and type and severity of environment is presented. Results indicate significant reduction in lifetime as a function of rising hold time for specimens charged with hydrogen, whereas a parabolic trend was observed in the case of specimens tested in air and in the presence of simulated marine environment Compared with baseline tests in air, a gradual reduction in lifetime was observed as a function of increasing concentration of hydrogen in the specimens. Micrographie, atomic force microscope, and scanning electron microscope analysis is performed to study the various aspects of AF1410 lifetime. Copyright © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.