Results of hydrogen-assisted fatigue lifetime testing indicated a substantial but gradual increment in crack growth rate as a function of increasing hydrogen content. Hydrogen was introduced into both sides of the specimen simultaneously via galvanostatic charging. Extensive scanning electron microscope fractographic analyses revealed a clear shift in the modes of failure and changes in fracture surface morphology as a function of increasing hydrogen content. A methodology is outlined that can be used to predict fracture surface features as a function of applied stress intensity factor. A convenient deterministic model is proposed that seems to reasonably accurately capture the crack growth rate behavior under strain controlled testing conditions. In addition, successful application of acoustic emission technique to classify various cracking stages in full spectrum testing was performed on hydrogen charged samples. Copyright © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.