Abstract: A method of effecting froth flotation in a receptacle divided by separating means to provide a plurality of flotation cells arranged one above another comprises passing froth upwardly from a first cell into a second cell situated thereabove while controlling the thickness of the froth layer in the first cell to correct variations therein and thereby inhibit coalescence. Apparatus for use in said method comprises a receptacle divided by separating means to provide a plurality of flotation cells arranged one above another, said separating means being adapted to provide, in operation, passage means for the passage of froth upwardly from a first cell into a second cell situated thereabove, the first cell having control means which acts to control the thickness of the froth layer in the cell in response to a variation in the thickness of said layer.