A continuum model of nanocrystalline copper was developed based on results from independent atomistic calculations on 11 bicrystals containing high angle grain boundaries. The relationship between grain boundary structure and its mechanical response was investigated. Based on the atomistic calculations; a constitutive law for grain boundary interfaces was implemented within a finite element calculation that consisted of a microstructure loaded in compression. The yield strength as a function of grain size was compared to experimental data and molecular dynamics results. Calculations were performed to demonstrate the relationship between intragranular plasticity and grain boundary sliding. (c) 2005 Elsevier Ltd. All rights reserved.