The curve matching method given by Cagniard (1953) to interpret magnetotelluric data in terms of layered resistivity models requires a set of master curves for two, three, or more layers, In this paper the master curve technique is extended to include the theoretical developments of Wait (1962) and Price (1962) in which the dimensions of the inducing field are considered as well as the vertical distribution of resistivity. A large number or two- and three-layer master curves are given for the interpretation of field data. The calculations were done on a computer using the formula given by Srivastava (1965). Curves for both apparent resistivity and phase are plotted as functions of period for various values of horizontal wave-length of the source and various layered models. Sorne cases in which it is difficult to interpret magnetotelluric data by master curves are mentioned.