Laboratory undrained cyclic shear behavior of silts has been studied by means of undrained cyclic stress - controlled ring shear tests. The dynamic behavior of silty soils on predetermined sliding surfaces in slopes with different gradients and various stress conditions were investigated. Four different initial stresses corresponding to slope angles (θ) of 0◦, 10◦, 15◦, 20◦ were examined. As for seismic force that drives the slope downward a the driving cyclic shear stress with the constant amplitude according to simulated static conditions of a sliding surface was considered. Liquefaction potential of non-plastic silt and non-plastic silt — kaolinite mixtures along with potential of either limited or catastrophic deformations were evaluated. Furthermore, the loss of shear resistance and pore water build up in relation to a number of cycles was observed. For both non-plastic silt and silt of 5% clay content, there is the significant effect of the initial static driving shear stress on their dynamic behavior. An increase in an initial slope gradient is associated with an increase of the shear resistance similar to behavior of sands. Excess pore water pressure generated similarly for both non-plastic silt and silt of 5% clay content.