The crack growth process in the high-velocity impact of water ice was directly observed with an image-converter camera which stored 24 successive images at speeds of 2¿105 and 5¿105 frames/s. At lower-velocity impacts, the maximum growth velocity of a crack was found to be 1050¿130 m/s. At higher-velocity impact experiments, 140-650 m/s, a shear fracture region was observed to grow from the impact point hemispherically with a velocity between 2.0 and 3.5 km/s depending on the impact velocity, which is larger than the shear wave velocity of water ice, 2.05 km/s. Then the fracture velocity gradually decreases, and the growth of the shear fracture region stops when the growth velocity is below 1 km/s, whereas radial cracks continue to grow outside the region. The subsequent radial growth of cracks was similar to that found at lower-velocity impacts. ¿ American Geophysical Union 1995