The mesoscale oscillatory baffled reactor (meso-OBR) is a novel technology for reaction engineering and screening applications. The meso-OBR exhibits high degrees of plug flow at low and moderate net flow rates (0.3-8 mL/min). For example, central and integral baffle configurations give good plug flow at net flows of Re-n = 4.3-34 for psi = 4-8 and psi = 5-10, respectively using St = 0.4-0.8. Recently, the batch equivalency of plug flow has been exploited to screen multiple equivalent batch reactions in a single experiment, minimising waste generation and reducing process development time. In addition, good multiphase mixing has been demonstrated using a variety of baffle configurations, presenting a wide range of potential applications for the technology. In this review, the characteristics of the mesoreactor that are beneficial for rapid process screening are explained. The results of all public domain reports of the use of mesoscale OBRs for screening are reported and the outlook for the technology is discussed. Throughout, the technology is compared and contrasted with the findings for "conventional scale" (>15 mm diameter) OBRs. A variety of case studies are used for illustrative purposes. (C) 2014 Elsevier B.V. All rights reserved.