A procedure is suggested to determine several properties in parcial differential equation of the parabolic type. The method is applied to the determination of thermal diffusivity and thermal conductivity of materials, using the measured transient temperatures in a special porbe. Another propertye to be determined is the thermal contact conductance between the probe and the material in a bulk. The properties are found by making the measured temperatures match the calculated temperatures in a least-squares sense. The method described is flexible enough to treat the special case of temperature dependent properties although only the case of constant properties has been verified. This method utilizes the solution of the heat conduction equation obtained by the Crank-Nicholeon method and by the method of particular solutions. The sensitivity coefficients can be utilized to gain insight in the method and they are utilized in order to have the probe built. The procedure is applied to nylon. Some results in simulated as well as in real experiments are presented and new experiments are suggested.