Plasticity spans many length and time scales. Permanent deformation of metals at the macroscopic scale is governed by the collective motion of many atomic defects (dislocations), with all scales in between affecting this process. Studies of plasticity on the various relevant scales has led to concepts such as phenomenological macroscopic plasticity, crystal plasticity and dislocation plasticity, in order of decreasing length scale. Although each of these have some success in explaining and predicting phenomena on their own pertinent length scale, the coupling between them, across the various scales, is still in its infancy. Forging a link between these concepts poses fundamental issues on how to retain relevant averaged information when going from a small to a larger size scale, and from discrete to continuum formulations. This volume contains the proceedings of an international conference dedicated to these issues.