Mature outer hair cells of the mammalian cochlea express a molecular actuator, prestin, which determines cochlear sound amplification. Prestin (SLC26A5) is a low efficiency electrogenic chloride-bicarbonate antiporter (Mistrik et al, 2012) and we have previously suggested that the mechanoenzyme properties of prestin arise from transitions between substates of the transport cycle (Muallem & Ashmore, 2012). Although fluxes of other radiolabelled anions have been used as substitutes for chloride (Bai et al, 2009) we report here using direct chloride imaging techniques on whether chloride transports is separable from prestin’s mechanoenzyme role. In order to image chloride fluxes, we have used either YFP or pHluorin (a pH-sensitive enhanced GFP) linked to the cytoplasmic side of prestin and expressed in CHO cells. Elevated intracellular chloride was signalled by a fluorescence quenching and changes in pH were minimized. Transfected cells, characterised by a ring of plasmamembrane fluorescence, were imaged at 0.2 Hz while being continuously superfused with differing levels of chloride solutions in constant 23 mM bath bicarbonate. Without prestin expression there was no measureable movement of chloride in CHO cells. When prestin was expressed in the cells, changes in fluorescence depended upon the chloride gradient across the cells membrane. In order to calibrate the flux rates, cells were patch-clamped with pipettes containing either 5, 15, 45 or 130 mM Cl (Clo replaced with gluconate) and the change in fluorescence measured on break-in to whole-cell, and determined the initial internal Cli of the cells, held in normal extracellular Clo, to be 18 mM. The fluxes were measured using pHluorin as the sensor and modelling the data indicated that the quench fluorescence curve had IC50=24 mM. To convert the fluxes to a prestin turnover, we used a mean prestin number of 2.5×105 per cell. The prestin turnover so determined was 900 prestin-1 s-1. It is known that extracellular salicylate, a blocker of prestin’s non-linear capacitance (NLC) and actuator properties, reduces the NLC by over 90%, and is compatible with a competitive block of an intracellular chloride binding site with a Ki =200 μM (Oliver et al, 2001). However 10 mM salicylate pre-applied to the to the bath reduced the YFP measured chloride flux by only 30%. There was a minimal shift in the fluorescence due to pHi changes induced by salicylate.These data suggest that the hypothesis of a single mechanical step in the prestin transport cycle requires elaboration.