Studying responses of live cells to agonists, antagonists and other physical stimuli offers insight into their complex membrane and internal biochemistry. An experimental technique has been developed in which responses of living cells in an inverted radial flow chamber are continuously monitored while being repeatedly stimulated using controlled pulses of a biologically active ligand. Precisely defined flow conditions result in reproducible peaks which can be numerically analysed by comparison with a tracer curve obtained by substituting a dye for the stimulus. Exploratory studies have demonstrated that the flow injection technique can provide a novel method for kinetics of receptor binding and cellular responses. Flow injection microscopy (FIM) allows identification of biologically active ligands and their ranking based on measurement of the cellular responses in a short time frame. The use of FIM for rapid drug screening, through monitoring of the initial kinetics of cellular responses, is demonstrated on a model system.