A vacuum cleaner includes a pair of low efficiency cyclones connected upstream of respective groups of high efficiency cyclones by respective elongate ducts. The high efficiency cyclones of each group can be arranged in a line or a cluster extending away from their respective low efficiency cyclone, such that at least a portion of one side of the low efficiency cyclone is exposed. The high efficiency cyclones can be connected to their respective elongate ducts at respective positions along the length thereof, with each cyclone comprising an inlet connecting to the duct. The inlets of each high efficiency cyclone can be stepped along the axis of the duct with respect to the inlet of each other cyclone of the group, in a direction which extends across the width of the duct.