The influence of various factors on the elution of sugars from charcoal columns by concentration gradients of organic substances dissolved in water can be readily explained, to the first approximation at least, by considering the sugar and the desorbing agent as competitors for the same active surface. It is possible to predict the behaviour of various systems on this hypothesis and to show how various types of separation can best be achieved. It is possible to separate the series of cello-oligoglucosides from acid-hydrolysed cellulose with the minimum of manipulation by using suitable conditions suggested by this study.