The specificity of strain behaviour of pipeline steel depending on the hydrogen concentration in bulk of metal was studied. The existence of some characteristic value of the hydrogen concentration at which the mechanism of hydrogen influence changes, namely: below this value the enhanced plasticity (decreasing of the yield stress value) takes places and above - the hydrogen embrittlement occurs, was shown. This value can be considered as an important engineering parameter for strength and fracture assessment of materials and structural components in hydrogenous environments and also at the development of technology of hydrogen treatment of materials with the aim of improvement their service properties. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.