The authors describe electroactive microwells which exploit highly localized electrokinetic effects in order to actively concentrate, confine, store, and reject particles in well defined geometries. In this letter the authors present experimental results demonstrating repeatable trapping and repulsion of polystyrene particles in wells ranging in diameter from 6 to 20 μm in the presence of a superimposed pressure driven flow. A comprehensive finite element model is developed to describe the transport physics involved in the attraction and repulsion processes. Immediate applications include active cell trapping, particle concentration and unlabeled sensing. © 2007 American Institute of Physics.