Simultaneous determinations exploiting the rates of reactions of different analytes with a common reagent, often referred to as differential kinetic analysis, is efficiently implemented in the flow analyser. To this end, specific strategies for pumping, commuting and/or detecting have been proposed. This review critically discusses the potentialities, limitations and application ranges of the different flow systems designed to accomplish differential reaction- rate methods, with emphasis to those involving spectrophotometric and luminometric detection.