A stagewise model is presented for the design of countercurrent liquid-liquid extraction columns allowing for breakage and coalescence. Backflow in the continuous phase is considered, and the nonideal behavior of the dispersed phase is described in terms of the drop-size distribution and individual drop velocities. The drop-size distribution, and dispersed-phase holdup are determined along the column. The model is applicable for any equilibrium relationship and allows for the variation in the physical properties of the phases along the column. Examples are given for different types of columns.