The continuous-flow transesterification of soybean oil with methanol using a rotating packed bed (RPB) for the production of fatty acid methyl esters (biodiesel) is presented herein. The RPB, which provides high centrifugal force and has an adjustable rotational speed, is employed as a novel transesterification reactor. In this Study, biodiesel is synthesized via the methanolysis of soybean oil using potassium hydroxide as the catalyst. The following variables were investigated for their effects on transesterification efficiency: the methanol-oil molar ratio, the estimated hydraulic retention time, the rotational speed of the packed-bed rotator, the reaction temperature, and the catalyst dosage. The yield of the fatty acid methyl esters (Y(FAME)) in the RPB system depends significantly on the experimental conditions, which influence the residence time distribution, the transesterification reaction rate, and the micromixing intensity. Due to its excellent micromixing characteristics, the RPB system shows satisfactory transesterification efficiency. The values of Y(FAME), productivity of FAMEs (P(FAME)), and P(FAME) per unit reactor volume (P(FAME)/V(R)) in the RPB are used to evaluate the performance for biodiesel production and allow for further comparison with other continuous transesterification reactors. Consequently, a RPB is considered a practical transesterification reactor with high transesterification efficiency. (C) 2009 Elsevier Ltd. All rights reserved.