Bubble load and top of froth measurements per size class were carried out in a rougher flotation circuit containing sulphide copper minerals and pyrite. This circuit consists of four parallel banks of seven 130 m(3) mechanical cells. Results of testing the first rougher cell (approximately 69% Cu recovery), showed that 40-60% of pyrite in the finer class of the concentrate (-45 mu m) was recovered by entrainment. For the coarser classes, pyrite was preferentially recovered to the concentrate by true flotation or association. These results were validated by batch flotation tests, using the same feed material to the rougher flotation circuit. The bubble load and top of froth measurements permitted the evaluation of the pyrite transport mechanisms at industrial scale, providing estimations of pyrite true flotation and entrainment which are relevant for pyrite depression evaluation. (C) 2014 Elsevier Ltd. All rights reserved.