Sandwich hologram interferometry was examined for ap-plicability to the nondestructive testing of high pressure nuclear reactor components. A nonnuclear valve was used as a test specimen. While new and unflawed, it was examined and holographically characterized under the stress of pressurization. A flaw was then machined on the inside surface of the valve casing, and the valve was reexamined. This procedure was repeated, deepening the flaw each time, until it was visible as a "chink" in the fringe pattern characteristic of normal valve expansion. From this, a sensitivity limit for interferometric detection of subsurface voids has been established. Cracks were not examined because the difficulty and expense of the simulation techniques did not fit within the scope of this contract.