For the transient heat conduction of a thin slab, the temperature-time history of its mid-point can be determined from a plane wall theory, provided that a slab thickness to length ratio of 0.2 or smaller is used in the experiments. Using the theory, two data reduction methods are described for deducing the thermal properties of conductivity κ and diffusivity (α) simultaneously from a single transient heating experiment. The first method uses an analytical technique to fit the inflection point on the temperature-t history plot to the theoretical inflection point. The second method, which was earlier proposed by the authors, uses a statistical curve fitting procedure to obtain the best fit between theory and experiment over seven points on the temperature-time history. Comparisons of the κ values obtained by these methods against steady-state heat conduction measurements of the same slabs for various building construction materials indicate good agreement, and give support to the validity of these procedures. The values of κ and α obtained by these procedures also compare favourably with reported literature data.