Most high strength steel and titanium alloys have been observed to have a threshold stress intensity, below which no environmentally-induced cracking occurs. Recent models for the concentration of atomic hydrogen in the vicinity of a dilatational stress field can be used to predict such threshold stress intensities. These models can predict state of stress effects which can be changed by yield strength, thickness and loading mode. The following analysis demonstrates how an externally applied hydrostatic pressure should increase the threshold stress intensity. A predicted increase of 5000psi-in 1 2 in an alpha-beta titanium alloy is in reasonable agreement with experimental observations of Dehart and Liebowitz.