In this thesis, various transmitter power control schemes are developed for different purposes of cellular mobile systems. The main objective of power control is to maximize system performance while maintaining adequate transmission quality. In the beginning, a mathematical programming model is introduced to understand the transmitter power control problem precisely. Some efficient solution procedures are proposed. Compared to existing reference power control methods, they achieve about 30% reduction in the blocking probability that measures system performance. To overcome some implementational drawbacks of the previously proposed methods, a simple distributed power control scheme is suggested and its convergence is proved. In addition, a simple instability detection rule is suggested. The proposed distributed power control method with the detection rule converges very fast, which can be applied to fast fading radio propagation environments. A forward link power control method for a CDMA radio system is also provided, which overperfoms the conventional fixed power control method by serving six more mobiles under the same bit error rate.