Pulp chemical conditions :pH, E(h), O-2 levels, conductivity, concentration of cations and anions, particle size and shape were measured in conventional and autogenous circuits of a plant treating a low grade copper ore. Results of particle size and shape analyses and pulp chemical conditions show some differences for the ores treated by conventional and autogenous circuits. But the plant scale flotation recoveries of copper were the same (88%) for both the grinding circuits. In laboratory flotation tests the recoveries of copper were much less (75%) and were also independent of the grinding method.