New applications of a flow-calorimetric biosensor system, the enzyme thermistor (ET) are described. The ET measures the reaction heat in a small column containing immobilized biocatalyst as a temperature change of the effluent from the column. Since most biological reactions are exothermic, the ET has a very broad applicability and numerous assays of clinical as well as biotechnological interest have been studied. The procedure is well suited for monitoring and control of biotechnological processes due to its high operational stability. New results from this area are presented as well as developments on an automated thermometric immunoassay (TELISA). Miniaturized ET devices are suitable for portable monitoring of, for instance, blood glucose. Other recent work includes determinations in organic solvents, direct characterization of immobilized biocatalysts and monitoring of bioactivities in solution.