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Residual stresses have in the past been introduced to manipulate growthrates and shapes of cracks under cyclic loads. Previously, the effectiveness of shotpeening in retarding the rate of fatigue crack growth was experimentally studied. Itwas shown that the compressive residual stresses arising from the shot peening processcan affect the rate of crack growth. Laser Shock Peening can produce a deepercompressive stress field near the surface than shot peening. This advantage makes thistechnique desirable for the manipulation of crack growth rates. This paper describesan experimental program that was carried out to establish this effect in which steelspecimens were partially laser peened and subsequently subjected to cyclic loading togrow fatigue cracks. The residual stress fields generated by the laser shock peeningprocess were measured using the neutron diffraction technique. A state of compressivestress was found near the surface and tensile stresses were measured in the midthicknessof the specimens. Growth rates of the cracks were observed to be moreaffected by the tensile core than by the compressive surface stresses.