Pavements are constructed on compacted soils that are typically unsaturated with degrees of saturation varying from 70 to 90%. Under unsaturated conditions soil matric potential can be regarded as an independent stress state, due to the contractile surface at the solid-liquid interface thus having a significant effect on soil strength. Pavement design research has begun to take into consideration the contribution of matric suction to the shear strength of soils. This study evaluates the effects of soil matric potential on shear strength of 4 soils. These soils cover the range of pavement subgrade types found in Minnesota including a high silt (80% silt), and a high clay (75% clay) soil. Shear strength was measured on remolded cylindrical soil cores 3.81 cm diameter by 8.64 cm long compacted at optimum water content to standard Proctor density. The remolded soil cores were saturated and then desorbed to a given suction before running triaxial shear test. Shear strength was measured at three confining pressures (70.3, 281 and 562 cm). Soil cohesion and internal angle of friction at each suction were computed for a pair of confining pressures using the Mohr-Coulomb failure criteria. Each test was run in triplicate. At low suction, shear occurred in a dilation mode (lateral expansion of cylindrical cores) while there was more distinct shearing angle at high suctions (≥ 1000 cm). The results showed a relationship between normal stress, deviator stress, and soil matric suction. Soil cohesion increased and angle of internal friction decreased with increasing suction. The data is being used to test Unsaturated Soil Mechanics theory of Fredlund that treats suction as an independent stress state with influence only on soil cohesion. This is in contrast to Bishops' treatment, which assumes suction affects normal stress only.