This document presents an overview of the investigations performed within the project NEWAC on the application of active flow control by aspiration to axial compressors. It is based on the measurements performed on different annular cascades, tested in the non rotating annular wind tunnel of EPFL in cooperation with the project partner ECL. In parallel to these measurements, both predictive and a-posteriori CFD simulations were performed by the project partners at SNECMA and ONERA. Several configurations were investigated in the annular wind tunnel with and without aspiration, on the hub or/and on the blades. For each cascade configuration, different inlet flow conditions were applied for several aspiration ratios. This yielded a large database of results that allows detailed analysis of the various influences by cross comparison of different cases. The applied measurement techniques included five-hole-probe measurements, Laser Doppler Velocimetry as well as pressure tap measurements on hub, casing and blades. The investigations gave an insight into the fluid mechanisms involved with the application of aspiration on blades and hub of an axial compressor rotor geometry. Since the flow structure resulting from simulations and experiments appreciably agree, the simulations significantly support the understanding of the flow mechanisms involved with the application of aspiration to the cascades. A selection of results, comparisons and conclusions is presented.