This project involved detailed sampling from an individual flotation cell as well as sampling of concentrates and middlings from cells in the rougher and scavenger flotation stages. The study shows how the total mass distribution and the distribution of galena and sphalerite change in the course of rougher and scavenger flotation. These changes have been evaluated in terms of flotation kinetics, and the residual quantity functions for galena and sphalerite in rougher and scavenger flotation are given. The frequency distribution of flotation activity has also been obtained for galena and sphalerite in rougher and scavenger flotation.