A geometrical modification of the well-known Sulzer SMX (TM) static mixer, the new SMX plus (patent pending), is found to lead to significant improvement of the mixing performance. Using a reduced number of bars, and gaps between the bars, the pressure drop of the mixer can be reduced to less than 50% while the mixing quality after a given number of elements remains nearly equivalent with the original SMX. CFD simulations are being relied upon to show the performance of the SMX plus both with regard to pressure drop, mixing quality and residence time distribution. These results are confirmed by LIF measurements. The mixing performance for streams with strongly different viscosities is investigated using a decolorization technique. Finally the dispersion behavior of this new mixer is measured. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.