Coherent frequency-domain equalisation (FDE) of DS-CDMA signals suffers from channel estimation error. Frequency-domain differential detection and equalisation (FDDDE) for the reception of differentially encoded DS-CDMA signals transmitted over a frequency-selective fading channel is proposed. At a transmitter, the differentially encoded data symbol is spread and transmitted. At a receiver, differential detection, equalisation and despreading are simultaneously performed in the frequency-domain. Compared with that of coherent FDE, FDDDE is much more robust against fast fading.