Numerical studies were performed using low Reynolds number k-epsilon turbulence models to examine the effects of unequal opposing jets on the flow pattern and mixing characteristics in a three-dimensional in-line static mixer utilizing confined turbulent opposing jets. Unequal jets were achieved by varying the mass flow rate ratio and/or inlet channel jet width ratio of opposing jets. It is found that, as compared with equal jets, two asymmetric recirculation bubbles are formed after jet impingement and a higher level of turbulent kinetic energy is produced in the impingement region as well as its vicinity. Result shows that better mixing is obtained for unequal jets than equal jets for the same total mass flow rate. (c) 2005 Elsevier B.V. All rights reserved.