Abstract:A new expression for the Bit Error Rate(BER) of a Direct-Sequence Code-Division Multiple-Access (DS-CDMA) system with non-ideal channel estimation in a frequency-selective Rayleigh fading channel is derived and evaluated. The analysis assumes an arbitrary number of independent, but non-identical resolvable paths combined by the conventional Maximal Ratio Combining(MRC) algorithm which is known to produce maxi-mal signal-to-noise ratio for diversity channels with equal noise powers and perfect channel estimates. The results obtained show that in such systems, the effects of non-identical fading and the channel estimation error on system performance cannot be ignored.