Error quantities, defined earlier to estimate the accuracy of texture measurement, are used to define a probability criterion for correct indexing of powder diffraction diagrams. The criterion is based on the compatibility of pole density distribution functions of different (hkl) depending on the directions {θ,γ}(hkl) of the reciprocal lattice vectors r*(hkl). The criterion was applied to permutation of the indices and variation of the angles {θ,γ}(hkl) in the vicinity of the correct values. In fortunate case, these angles can be determined within a few degrees by minimizing the error quantities. The method works very well with strong textures but it is still applicable if only weak textures can be achieved. The method was tested with different crystal symmetries including cubic, hexagonal, orthorhombic, and monoclinic. It is concluded that the criterion can be successfully applied to all crystal symmetries. If a measuring technique based on a position sensitive detector is used, even multifold peak superpositions in tilted sample orientations can be resolved. The method can also be applied if some (hkl) cannot be separated experimentally.