Liquid wastes in unprecedented quantities are expected to be injected below the land surface because of recent stringent controls on disposal to streams. Some of the possible consequences of waste injection are (1) groundwater pollution, (2) surface-water pollution, (3) changes in rock permeability, (4) subsidence, (5) earthquakes, and (6) mineral-resource pollution. Although much work has been done to predict some of the effects, the current state of knowledge is not adequate to estimate them accurately. Theory regarding (a) dispersion, (b) nonlinear relations between rock stress and strain, and (c) interrelations of hydraulics, heat, chemistry, and rock mechanics at macroscale is especially deficient for application to the waste problem. Advances in the chemical thermodynamics and kinetics of geochemistry may provide improved technology.