A modified heat-flux, computer-assisted bench calorimeter is described for continuous in situ measurement of heat generated during the growth of microorganisms in submerged cultures under std. lab. conditions of temp., aeration, agitation, and pH. The calorimeter does not rely on heat balance and makes insulation of the app. unnecessary. The modified calorimeter is sensitive enough to permit accurate and easy monitoring of the heat dissipated by a weakly exothermic culture of Escherichia coli under stirred and aerobic conditions. [on SciFinder (R)]