Three-dimensional serpentine micromixer (TSM) has been well known to be an attractive design because of its simple fabrication and efficient mixing performance, but its basic characteristics have not been fully investigated nomithstanding several reports in the past. The present article comprehensivel y investigates flow and mixing characteristics of TSM. Three major mixing mechanisms are identified, namely rotation, lamination, and chaotic advection. The mixing performance of TSM is analyzed and compared in terms of the three mechanisms by means of numerical analysis with three representative types as examples of TSM: (1) serpentine type C; (2) serpentine type L; (3) improved serpentine laminating micromixer. Numerical analysis system based on a finite element method and a colored particle tracking method enables not only flom, visualization but also computation of Poincare' section and Lyapunov exponent a dynamical system analysis of TSM. (c) 2008 American Institute of Chemical Engineers.