We investigate experimentally the macromixing behavior of two liquids in a multi-orifice-impinging transverse jet mixing that has four orifices embedded symmetrically on the wall of the mixing pipe, using the PLIF technique. We found that when the velocity ratio of the injected streams B in the orifices to the cross flow A in the pipe, r, reaches a certain value, the impingement among Streams B occurs and leads to substantial enhancement in the mixing performance. As r increases, the impingement location moves backwards closer to the injection plane, and eventually direct impingement among Streams B occurs, leading to part of Streams B jumping upstream, which is referred to here as back-splash. The mixing time reduces as r increases. When the back-splash occurs the mixing time reduces to a plateau. Effects of the Reynolds number and diameter of the mixing pipe on the mixing performance and back-splash have been also investigated. (C) 2013 Elsevier B.V. All rights reserved.