This article presents an adaptive digital predistortion (DPD) for linearizing RF power amplifiers (PA). The idea is to use nonlinear curve-fitting in conjunction with the look-up table to adaptively pre-adjust the gain and the phase of the input data before it is fed to the amplifier. The performance of the algorithm is tested by simulation. The input data is that of the standard IS-95A test signal and the data used to simulate the nonlinear characteristics of the device is measured from a 30 watt commercial CDMA PA operating at 50 watt. The results showed that based on the software-modeled PA, the algorithm can be used to adaptively adjust the input data so that the PA appears linear.