The National Institute of Standards and Technology (NIST) and the Center for Better Living have formed a collaboration to assess the performance and failure mechanisms of gypsum wall assemblies under real fires/furnace conditions. These measurements are being used to compile an experimental database necessary to validate models that could be used to predict their performance and ultimate failure under various design fires. A critical component of the database is thermal property data of gypsum board. The present paper describes the results of an effort to quantify thermal properties of gypsum board. The thermal conductivity specific heat mass loss and linear contraction for gypsum board types widely used in the U.S.A. and Japan were measured both at room temperature and at elevated temperatures. The gypsum board types tested include Type X and Type C from the U.S.A. and Type R and Type F from Japan. Results indicate that the difference in thermal properties of all gypsum board samples tested in the present study is not significant particularly at elevated temperatures. A large difference in linear contraction among gypsum board samples was observed at elevated temperatures, implying a significant difference in mechanical behavior at fire temperatures. The experimental data set provides valuable information that can be used to model the behavior of gypsum board at elevated temperatures. Copyright © 2009 John Wiley & Sons, Ltd.