Using the mapping method an efficient methodology is developed for mixing analysis in the rotated arc mixer (RAM). The large parameter space of the RAM leads to numerous situations to be analyzed to achieve best mixing. and hence, it is indeed a challenging task to fully optimize the RAM. Two flow models arc used to study mixing: one based oat the full three-dimensional (3-D) flow field, and a second one based oat a simplified 2.5-D model, where art analytical solution is rued for transverse velocity components in combination with a Poiseuille profile for the axial velocity component. Detailed 3-D velocity fold analyses reveal locally significant deviations font the Poiseuille profile e.g., presence of back-flow, but only minimal differences in mixing performance is found using both floes, models (3- and 2.5-D) in the RAM designs that are candidates for accomplishing chaotic mixing. Despite the computational advantage of the 2.5-D approach over the 3-D approach, it is still cumbersome to analyze mixing for large number of designs using techniques based on particle tracking, e.g., Poincare sections, dye traces, stretching distributions. Therefore, in this respect the mapping method provides an engineering tool able to tackle this optimization problem in all efficient way. Oil the basis of mixing evaluations, both in qualitative and quantitative sense, for the whole range of parameter space. the optimum set of design and kinematical parameters in the RAM is obtained to accomplish the best miming. (C) 2008 American Institute of Chemical Engineers AIChE J, 54: 2809-2822, 2008