In many efforts to increase the efficiency of power amplifiers of mobile terminals, compensation of nonlinear distortion based on an adaptive predistortion method has performed an important role. In the course of basic evaluation of a method using a look-up table (LUT) and a method using an approximation for compensation of nonlinear distortion, a newly developed method using approximation and a ROM type LUT with a small-sized memory has been proposed to overcome barriers to practical application and disadvantages associated with the LUT method. Experimental trials of the proposed method were applied to narrow-band digital modulation systems. As a result, the proposed method was found to provide a satisfactory capability of compensating nonlinear distortion, with next adjacent channel interference of less than -55 dBc. The proposed method has advantages such as a small memory size and excellent RF performance, and is expected to occupy an important position in many adaptive predistortion methods.