The goal of performing sensitivity analysis of a simulation model is to determine the effect of input variation and the effect of input uncertainty on the output data. Sensitivity analysis is an unavoidable step in model validation, and it is also generally useful in performing simulations. The user must know the influence of the accuracy of the data that is input to the program. This paper presents a methodology for performing sensitivity analysis as well as the tools that implement this methodology, MISA and LiSA, that were developed within the IEA-ECBCS Annex 23 ＇Multizone air flow modeling＇. The basic concepts of sensitivity analysis as well as the main characteristics of the developed tool are presented. More detailed information are available in the final report of the sub-task 3 ＇Evaluation of COMIS＇ of the Annex 23 [J.-M. Furbringer, C.-A. Roulet, R. Borchiellini, Evaluation of COMIS, final report IEA.ECB & CS Annex 23 Multizone Air flow Modelling, LESO-PB, EPFL, 1015 Lausanne, Switzerland, 1996.].