Abstract A review of numerous experimental data sets for frictional materials has led to a reformulation of the condition for plastic yielding in such materials. A yield function is proposed such that yield surfaces are equivalent to plastic work contours. Two parameters are required in this function. The yield surface resembles an asymmetric tear drop in the principal stress space. It includes tensile behavior of materials with effective cohesion. Work hardening and softening behavior can be simulated through the formulation of plasticity proposed herein. The capabilities of this mathematically consistent formulation are examined by comparisons with experimental data from two- and three-dimensional tests on different frictional materials.