Due to their high efficiency, impinging streams, which involve the use of two inlet streams that enter the system through two closely spaced inlets along the same axis in opposite directions, have recently found many applications in the chemical and food industry as alternatives to conventional mixing operations. However, there is no prior work that focuses on the flow and mixing behavior of non-Newtonian impinging streams. Numerical simulation was therefore performed to investigate the flow and mixing behavior of steady-state, two-dimensional laminar confined impinging streams of shear-thinning fluids. The coupled heat, mass and momentum balance equations were solved with the finite element method using commercial software FEMLAB (TM) 3.0. The effects of various parameters, i.e., inlet jet Reynolds number based on the inlet slot width (Re-j) in the range of 10-200 and the flow behavior index of the fluids in the range of 0.6161-1, on the flow and mixing behavior of impinging streams were then investigated. Temperature of the mixing fluid was used as a passive tracer to monitor mixing in this study. The results were also compared and discussed with those of Newtonian impinging streams. (c) 2006 Elsevier Ltd. All rights reserved.