In situ X-ray diffraction experiments performed on nanocrystalline Ni demonstrate an evolution of intergranular stress with plastic deformation that is different from coarse-grained counterparts. Using a crystal plasticity model, the X-ray diffraction footprints are linked to violent intergranular stress redistributions and special distributions of critical strengths associated with quantized intragranular slip. The model offers an alternate view to other models based on the hypotheses of the role of grain boundary sliding at small grain sizes. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.