In this paper, we present a study of the bit error rate (BER) performance of chaos-based DS-CDMA system over an m-distributed fading channel. In this system, the perfect synchronization between receiver and transmitter is assumed. The transmitted bit energy after spreading by chaotic signal is not considered as constant in order to evaluate with precision the BER for such system. The performance of chaos-based DS-CDMA system is examined first in mono-user case. An approximation of the received bit energy by a known distribution leads to an accurate analytical BER expression. This BER computation approach is generalized for asynchronous multi-user case. The performance of DS-CDMA system using Gold sequence is compared and discussed to chaos-based DS-CDMA system. A perfect match between simulations and analytical BER expressions confirms the exactitude of our approach.