The fifth electron-cloud workshop, ECLOUD'12, will take place from 5 to 8 June, 2012 at La Biodola (isola d'Elba) Italy. The existence of the electron-cloud effect (ECE) has been firmly established experimentally at essentially all modern storage rings, either via performance limitations or by deliberate provocation. The ECE is a consequence of the strong coupling between a charged-particle beam and a cloud of electrons that inevitably develops inside the vacuum chamber. Resulting deleterious effects include beam instabilities, beam losses, emittance growth, increases in vacuum pressure, added heat load at the vacuum chamber walls, and interference with certain beam diagnostics. Electron-cloud effects are incompletely understood dynamical phenomena. While the fundamental mechanisms are well recognized and the qualitative picture clear, the phenomena involves many surface properties and geometrical parameters of the vacuum chamber coupled in a nontrivial way with the beam characteristics. In addition, the relevant time and energy scales span a wide range, and many of the essential parameters are not well known a priori. Hence the detailed prediction of ECE's at a given machine, not to mention the extrapolation from one machine to another, are subject to uncertainties. High-power microwave applications in modern satellites are perturbed by phenomena of multipacting and RF breakdown, which are governed by the same surface parameters as ECE in accelerators, which, especially for multi-carrier signals, exhibit very similar characteristics and electron-cloud build-up time scales, and which can be modelled by similar simulation tools.