Abstract It is shown that proof testing a vessel can provide assurance of subsequent service life; however, the test can cause subcritical flaw growth. This growth must be minimized through careful attention to the test procedures. Several case histories are described, along with experimental static fracture toughness and sustained stress flaw growth data. These cases include such materials as aluminum, steel and titanium alloys, in various media, such as liquid propellants and test fluids. Times to failure and rate of growth of flaws are discussed in the context of linear elastic crack tip stress intensity factors. The influence of hold time at maximum load on the cyclic growth of flaws is also shown. Fracture mechanics analyses, together with static and sustained load fracture specimen tests, and the conventional proof pressure test of the vessel can be, and have been, used successfully in the prediction of minimum pressure vessel lives and modes of failure.