The ductility, toughness, and resistance to tensile cracking of clays can be improved with the inclusion of short fibers. Tire buffings are derived from the tire retread process and because of their elongated shape, may be used as fiber inclusions. The objective of this study was to evaluate the drained and undrained shear strength of mixtures of clay and tire buffings. Mixtures of silty low plasticity kaolinitic clay and 10% by dry weight of tire buffings were compacted at both Standard and Modified compaction energy. Consolidated-drained and consolidated-undrained triaxial tests were run at confining stresses ranging from 50 to 300 kPa. Preshear and postshear permeability tests were conducted. Results showed that the peak strength of the composite is comparable to or greater than that of clay alone when tested at confining stresses below 200-300 kPa. Above this threshold, the presence of inclusions tends to degrade the strength of the clay. Changes in permeability were not significant. © 2007 ASCE.