Existing work on mineral solubility in fluid-infiltrated and stressed rock has remained limited in that it has neglected surface forces. These forces are appreciable only when the fluid exists as a thin film, as in the grain-to-grain contact zone and in microcracks. Indeed, when the film thickness is of the order of 10-9 m or so, the strength of the forces can be comparable to overburden stress at several kilometers depth. In this contribution we develop the thermodynamics of the phase reaction between nonhydrostatically stressed grains and an intervening water layer by using the concept of the disjoining pressure to account for surface forces acting in the grain-to-grain contact zone. Using a thermodynamic extremum principle, we find an extended version of Gibbs's classical condition for the equilibrium of a stressed solid in contact with its solution phase. We then employ nonequilibrium thermodynamics to formulate kinetic equations describing phase boundary migration and intergranular mass transfer. It is demonstrated that surface forces weaken the efficacy with which diffusion removes dissolved material from the grain-to-grain contact zone and enhance the tendency of intergranular pressure solution to flatten initially rough surfaces. ¿ American Geophysical Union 1995