Code Division Multiple Access (CDMA) is a multiple access scheme based on spread spectrum techniques, that has been used for many years for military communications, and quite recently for commercial applications, such as satellite and digital cellular radio communications. Certain inherent characteristics of spread spectrum, such as interference and multipath suppression capabilities, privacy, and more efficient spectrum reuse, make CDMA advantageous for mobile cellular communications. It is the intention of this project to provide an examination of how these properties of CDMA can be used to increase capacity comparing with conventional multiple access techniques. For this purpose, the capacity of a single-cell, power controlled, asynchronous direct-sequence (DS) CDMA system is first investigated using Gold codes and both binary and quadrature phase-shift-keying (BPSK and QPSK) modulation. The investigation carries on with the calculation of both the forward and reverse link capacity of a multiple-cell CDMA system by means of analytical calculations and Monte Carlo simulations. Finally, a straightforward comparison with conventional techniques such as FDMA and TDMA shows that CDMA can indeed provide much higher capacity.