The size-dependent yield stress observed in experiments on sub-μm metallic pillars was used to test theoretical models and thus permit the predictions of defect dynamics simulations to be compared directly with mechanical strength measurements. Although the depletion of dislocations from sub- μm face-centered-cubic pillars provided a plausible explanation for the observed size-effect, multiplication of dislocations in body-centered-cubic pillars was predicted by a number of molecular dynamics and dislocation dynamics simulations. Under the combined effects of the image stress and dislocation core structure, a dislocation which nucleated from the surface of a body-centered-cubic pillar generated one or more dislocations which moved in opposite directions before exiting the surface. The process was repeatable, so a single nucleation event was able to produce a much larger amount of plastic deformation than that in face-centered-cubic pillars. This self-multiplication mechanism suggested the need for differing explanations of the size-dependence of yield stresses in face-centered-cubic and body-centered-cubic pillars. Surface-Controlled Dislocation Multiplication in Metal Micropillars. C.R.Weinberger, W.Cai: Proceedings of the National Academy of Sciences of the USA, 2008, 105[38], 14304-7