In spite of the large-scale industrial use of the acetone-butanol fermentation process earlier this century (until 1983 in South Africa), very little has been published on the inoculum preparation techniques required for successful fermentation using these bacteria. In particular, heat-shocking has often been referred to as "useful'' but no quantitative data are available. Data presented in this paper demonstrate and quantify the effect of heat-shocking on batch fermentation yields using one organism capable of this fermentation.