The enhancement of the dissolution rate of the sparingly soluble benzoic acid in aqueous solution by solid rotation, ultrasound and chemical reaction was investigated. The analysis indicated the strong influence of the ultrasound energy dissipation rate on the enhancement. The overall enhancements due to the three means were compared. The enhancement due to ultrasound was found to be much greater than mechanical rotation and comparable to that of chemical reaction. (C) 2004 Published by Elsevier B.V.