Mechanical behavior of materials at small length scales has received significant attention in recent years, due mainly to the development of devices and components having micro- and nano-scale feature sizes. In miniaturized structures, deformation is heavily influenced by the physical confinement imposed on the material. The present article is devoted to this type of constrained plastic deformation in metals. Continuum plasticity is used as a primary tool to describe the deformation features, for the purpose of establishing an overall mechanistic view which is often missing in the materials science community. We discuss recent progresses in understanding the externally influenced plastic flow behavior in selected metallic structures, including thin continuous films attached to stiff or compliant substrates, various forms of metal lines in modern semiconductor devices, and metallic joints in electronic packages. Special emphasis is on the evolution of local deformation pattern and overall mechanical response, and their implications in the interpretation of experimental results and the structural integrity for real-life applications. Aside from the review of current status of knowledge, we also address common misconceptions, remaining challenges as well as directions of future research in constrained small-scale plasticity. (C) 2008 Elsevier Ltd. All rights reserved.