The effect of fines recycling back to the rod mill in a conventional full-scale grinding circuit was evaluated. For this purpose, a fraction of the hydrocyclone feed stream was diverted to the rod mill feed. It was observed that operating with fines recycling allowed a decrease of 2-3% in the grinding product size, % +212 mu m, at similar solid feed capacity, tph, and similar circulating load in the ball mills. This represents a potential increase of about 1.0-1.5% in the overall rougher flotation recovery. The effective pulp residence time in the ball mills was evaluated and was found to be 1.6-1.8 min. Thus, the effective volume of slurry inside the ball mills was estimated and was equal to 32.7%. The product size, % +212 mu m, was correlated with the main operating variables such as Bond index, feed tonnage, power consumption and circulating load. The model was adjusted to describe normal operation without fines recycling. Then, the comparison of experimental data with fines recycling and those without it, showed a decrease of 2.5% in % +212 mu m, for the same feed capacity tph. (c) 2005 Elsevier Ltd. All rights reserved.