In practice, fothers are selected following general guidelines and verification by laboratory and/or plant tests. The terms “powerful” or “selective,” which are commonly used to characterize frothers, have intuitive rather than scientific meaning. A research program has been set out to study fundamental properties of the flotation frothers and to identify the tests which can provide information needed to characterize and classify such flotation agents. Since flotation frothers are used to reduce bubble size and increase froth stability, in the procedures adopted in this paper they were characterized by their ability to reduce bubble size in a flotation cell and to increase foam stability. It has been shown that the developed frother classification system based on these two measurements is able to correctly distinguish the frothers known as being selective from those which are known to be powerful.