Base-catalysed biodiesel production was continuously screened using new designs of mesoscale oscillatory baffled reactors. Experiments were carried out at very low flow rates, less than 2 ml/min, which would be in the laminar flow regime in non oscillatory, steady state. Initially central disc baffles and helically wound wires were used, but provided insufficient mixing at this scale as demonstrated by glycerol settling. A new design of sharp-edged, helically baffled reactor was developed specifically for this application, which exhibited homogeneous mixing in the two-phase liquid reaction even at these low flow rates and low oscillatory Reynolds numbers. Methyl ester (biodiesel) was produced at a consistent quality and there were clear responses to variations in input conditions. A clear step-change between various steady state molar ratios of methanol to oil and dynamic screening was observed in these mesoscale oscillatory baffled reactors. Rapid screening technique such as this has the potential to significantly reduce process development, operating costs and environmental impact. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.