This paper reviews some of the aspects of combining in situ/operando infrared spectroscopy and kinetic studies. The strengths and limitations of various methods are discussed based on examples found in the literature and especially taken from the present author. A clear warning is made that qualitative or semi-quantitative analyses can easily result in unimportant surface species being mistaken for true reaction intermediates. (C) 2009 Elsevier B.V. All rights reserved.