Though microreactors provide high heat transfer rates, temperature profiles are formed in case of fast and highly exothermic reactions. A method based on non-intrusive infrared thermometry has been developed to track these profiles quantitatively with a resolution of 250 data points/cm(2) and a precision of 1 degrees C. By placing the microreactor at a pressure of 10(-2) mbar, convective heat losses are efficiently suppressed which assures well defined boundaries and reproducible results. The temperature profiles of the fast and exothermic hydrolysis of tetraethoxysilane were measured inside a microcapillary at different flow rates via infrared transparent window. In the reactor provided with a cooling system, the heat transfer coefficient was determined by thermal imaging for different operating conditions. The data obtained are in good agreement with the values reported in literature. (C) 2012 Elsevier B.V. All rights reserved.