152 biopsies from the colon of healthy persons were incubated with several nutrition mediums in a microcalorimeter. The course of the heat-flow rate was measured at 1 min interval and graphically displayed as a function of time. For evaluation of the results, the maximum (P-max), the mean values (P), and the area under the curve as a measure of the total released energy (E-tot) of the power-time curves were determined. The mean enthalpy change of all samples over time was 3.9 mu W per sample. Depending on incubation conditions, mean values ranged between 2.5 and 7.1 mu W, maximal values between 3.5 and 13.3 mu W. The areas under the curve varied between 6.2 and 18.3 mJ. Our results also showed that bacterial growth can influence measured enthalpy changes if antibiotics are not present. Under identical incubation conditions, steel ampoules were better than glass ampoules with respect to methodic artifacts. We conclude that microcalorimetric investigations on bioptic material from colonic epithelium are possible. Interestingly, our measured enthalpy changes were lower than those expected from the oxygen consumption rates and other metabolic processes. The reason is yet to be explored.