Laboratory studies have shown that consolidated fault gouge dilates in response to an increase in the rate of shearing. During the period of accelerating slip that characterizes the onset of an instability, or earthquake, on a fault containing consolidated, fluid-saturated gouge, the accompanying dilatancy will result in a reduction in pore fluid pressure and an increase in effective normal stress. We report laboratory observations of a 3% drop in pore pressure per decade increase in sliding rate of quartz gouge between granite fault surfaces. This dilatancy strengthening is greater than intrinsic rate-weakening observed for dry gouge and can play an important role in earthquake nucleation.