For adaptive filters with long impulse responses and requiring modelling by an FIR filter, algorithms incorporating computationally efficient DFT-based adaptive block filters are the design of choice. The reduction in computational complexity is very significant in applications such as active noise control and the hands-free telephone system echo cancellation problem where impulse responses of more than a 1000 samples are common. The performance of frequency-domain adaptive algorithms is analysed and, when properly designed, shown to be equivalent to time-domain algorithms with uncorrelated input signals. The design parameters include: block length, DFT length and partitioning of the impulse response. The study includes both constrained and unconstrained parameter adaptation. Guidelines to the design of partitioned frequency-domain LMS (PFLMS) algorithms are given. Copyright (C) 2000 John Wiley & Sons, Ltd.