In the context of microwave enhanced chemistry, usually a narrow set of single and multimode cavities are considered as microwave field applicators. This study aims to widen this current scope by exploring the potential of rectangular waveguides as a basis for microwave applicator systems. It is demonstrated that such systems offer microwave field patterns that are relatively simple and predictable, which makes processing amenable for adaption to specific requirements and for optimization. The feasibility of long residence time continuous flow chemistries under microwave conditions is demonstrated in a novel reactor type that the rectangular waveguide uniquely supports. (c) 2012 Elsevier Ltd. All rights reserved.