Zimmermann, F. JACoW Geneva, Switzerland 978-3-95450-187-8 10.18429/JACoW-eeFACT2016-THS2H1 English 210-215 THS2H1 ion electron impedance feedback wakefield Contribution to a conference proceedings 2017 2017-07 https://doi.org/10.18429/JACoW-eeFACT2016-THS2H1 http://jacow.org/eefact2016/papers/ths2h1.pdf This paper summarizes the session on impedance issues and beam instabilities at the ICFA workshop on future circular electron-positron factories "eeFACT2016" held at the Cockcroft Institute, Daresbury, from 24 to 27 October 2016. This session also covered active beam stabilization by feedback systems. Beam-beam effects and coherent beam-beam instabilities were addressed separately and, therefore, are not included here.