Computational Fluid Dynamics (CFD) has been employed for the optimization of the mixing efficiency of a Kenics static mixer. A series of numerical simulations has been undertaken for non-creeping flow conditions to determine the optimal twist angle of the mixing elements. The mixer efficiency has been assessed by considering the computed pressure drop along the mixer and the size of the fluid structures remaining at the mixer outlet. Contrary to the results of previous investigations for creeping flows, it is shown that for the present non-creeping Bow conditions, the twist angle of 180 degrees employed in the standard Kenics design is optimal. It is demonstrated that CFD provides an invaluable tool for mixer design optimization, despite the significant computational resources necessary to undertake the present study. (C) 1999 Elsevier Science S.A. All rights reserved.