Modifications and improvements to the Nabetani-Rankin method of sequential layer addition for a one-dimensional earth are presented and applied to several representative models to demonstrate the technique developed for inversion of magnetotelluric data. The inversion process was aided by the use of computer graphics and interactive programming. It was found that there are general rules to be followed for choosing layer parameters, and once these methods are learned, the advantage and speed of interactive programming can be utilized. This method is inherently stable.