This paper deals with the research work being conducted at the Institute for Research in Construction of the National Research Council of Canada to Develop mathematical models for the calculation of the fire resistance of compression members, such as concrete walls, columns made with steel and concrete and composite steel-concrete columns. The various steps in the calculation procedure, namely the calculation of fire temperature and the thermal and structural response of the members, are discussed. Comparisons of results obtained with the models and test results are also shown for various types of columns.