In order to identify parameters of a chemical reaction, such as rate constants, reaction orders, activation energies, or reaction enthalpies, a new evaluation algorithm that allows a simultaneous evaluation of online measured infrared and calorimetric data will be investigated. The evaluation of the infrared data neither requires calibration nor the knowledge of pure component spectra. Overlapping absorption bands are allowed. The weighting of the calorimetric and infrared objective functions performs completely automatic using a sensitivity analysis. The performance of this combined evaluation principle was investigated by analyzing the consecutive epoxidation of 2,5-ditert-butyl- 1,4-benzoquinone with tert-butyl hydrogen peroxide. Different reaction models as well as physical constraints were postulated in order to reveal the flexibility and the capability of the approach. The results obtained underline the importance of such a combined evaluation of both analytical signals instead of separate evaluations. (C) 2004 Elsevier Ltd. All rights reserved.