Hysteresis in stream solute behaviour both poses problems and provides opportunities for the geomorphologist. The causes and controls of hysteresis are reviewed, and the complexity of hysteretic effects is illustrated from detailed data collected in several contrasting catchments in the United Kingdom and Switzerland. Variability in storm-period and annual hysteretic behaviour is described and the importance of various controlling factors is discussed. Trilinear plotting of data on water composition provides an effective means of summarising contrasting hysteretic effects for different ions, time scales and environments.