Lime slaking is important for its use in a number of industrial applications. There are normally a number of factors that can influence the rate of the hydration of lime, which include, amongst others, production and storage conditions and the constitution of the water used in the slaking process. This paper describes an investigation of the effect of mode of agitation during the slaking process of the limes from different geological origins. During the investigation normal mechanical shaking was compared with ultrasonic agitation when the limes were contacted with water. It was found that the ultrasonic shaking enhanced both the rate and the degree of hydration of the different limes being slaked. The geological origin of the various limes also exerted an influence in the slaking process. (C) 2003 Elsevier Ltd. All rights reserved.