The concentration of a low-grade porphyry ore by froth flotation in a 4.7-Cm-diam air-sparged hydrocyclone was investigated. The effects of important design and operating variables on the separation efficiency were examined. The variables included slurry feed rate, airflow rate, pulp density, cell length, wall porosity, and kerosine additions. Several modifications to the basic design of the air-sparged hydrocyclone were also studied. A comparison of performance of the air-sparged hydrocyclone with conventional flotation for this particular ore showed that remarkably short retention times were required to achieve satisfactory separations. Moreover, preliminary data indicated that the recovery of molybdenum and gold with the air-sparged hydrocyclone was comparable with that obtained in a conventional cell. It was concluded that the air- sparged hydrocyclone has the potential to significantly alter conventional copper rougher or scavenger circuits, although additional research will be required before this potential can be realized.