Mineral particle size plays a significant role on the flotation process. The flotation performance (grade and recovery) of apatite particles in a complex carbonatite ore from Brazil was investigated in a flotation column as a function of particle size and reagent concentrations. Flotation feed samples were also mineralogically and chemically characterized. For the bench scale flotation experiments, the sample was fractioned into different size intervals. The experiments were conducted according to a factorial experimental design. The experimental data were analyzed using P2O5 grade/recovery curves, response surface methodology and canonical analysis. An optimum particle size was found under the experimental conditions studied. The P2O5 grade and recovery rates obtained with a particle.size between 37 mu m and 105 mu m were simultaneously higher than those required industrially. (C) 2008 Elsevier B.V. All rights reserved.