The concentrator at Minera Los Pelambres currently processes 130,000 tpd of Cu/Mo ore. The rougher circuit originally consisted of four flotation banks. In August 2006 the rougher circuit was enlarged adding two flotation banks, each one consisting of 5 cells of 250 m(3). This paper describes the metallurgical comparison between the new flotation banks and the old ones (130 m(3) cells) operating in parallel. For this purpose, 5 overall mass balances were developed for a range of feed flowrate (4000-7000 tph). Thus, an effective comparison between the cell hydrodynamics, as well as the effect that the number of cells per bank has on the overall bank recovery, was developed. Also, the effects of internal launders on cells stabilization and mineral recovery were analysed. Results on mineral upgrade and recovery, per size classes, showed that the banks of 5 cells (250 m(3)) gave metallurgical results similar to the banks of 9 cells (130 m(3)). (C) 2008 Elsevier Ltd. All rights reserved.