Systems for fitting an implantable cochlear stimulator to a patient include an interface unit configured to display a graphical representation of an implant fitting line as part of a graphical user interface. The implant fitting line has a slope and a horizontal position and represents a mapping relationship between a plurality of audio frequencies and a plurality of stimulation sites within a cochlea of the patient. The interface unit is further configured to facilitate adjustment of the slope and/or horizontal position of the fitting line.