The aim of this paper is to study the laminar mixing induced by a quadripolar Stokes flow superimposed to an axial Poiseuille flow. When the two-dimensional quadripolar flow is twisted along the direction of the Poiseuille flow, advection becomes chaotic. This three-dimensional open flow device is applied to the mixing of a dye injected continuously on a fraction of the entrance section. (C) 2003 Elsevier Ltd. All rights reserved.