Samples of powdered (<150 &mgr;m) andesitic basalt, to which had been added 0-20 wt.% water, were subjected to shock pressures of 294--490 kb. The dry samples are completely lithified by the shock, with plagioclase crystals converted to diaplectic glass and partially bonded at the edges. The dominant effect of added water is a marked decrease in shock lithification, with samples containing 15--20 wt.% water remaining particulate after shocks of 296--430 kb. A secondary effect of water contents below 15 wt.% is enhancement of the production of vesicular melt glass. No glass was observed to have been found in the totally particulate samples which contained 15--20 wt.% added water. The instantaneous hydration and clay production predicted for impacts into water-bearing target materials were not observed in the present experiments.