In situ leach mining operations often encounter difficulty maintaining adequate leach solution flow into the ore formation. Swelling and dispersion of clay particles in the formation are often responsible for this permeability loss. Permeability and leaching tests were done in the laboratory on clayey ores to evaluate a clay- stabilizing polymer's effectiveness in preventing these problems. Test results indicate that treating the ores with the stabilizer could maintain permeabilities two to five times greater than the long-term permeabilities present in untreated ores. Both alkaline (ph 8.5) and acidic (ph 2.0) Leaches were used in the permeability- leaching tests. Since in situ leaching throughput rate is directly related to permeability, these results also indicate a potentially beneficial effect on operating parameters such as capacity and injection pressure. To determine the reasons for the success of the clay stabilizers, an investigation was conducted to determine the effect of the stabilizer on clay swelling and dispersion. Clay- swelling tests indicated that the clay stabilizer reduced clay swelling. Zeta potential measurements made on fine clay particles treated with the stabilizer were compared to measurements made on untreated particles and indicated that the stabilizer was electropositive and, therefore, could reduce the degree of negative charge on the particles and their tendency to disperse or migrate.