This study investigated the effect of fast-acting Automatic Gain Control (AGC) on the speech intelligibility of cochlear implant users as a function of presentation level. Both low and high signal-to-noise ratio conditions were investigated. The AGC substantially reduced the amount of clipping, but did not give consistent improvements in intelligibility. With no AGC, and high signal-to-noise ratio, speech scores were not significantly degraded until more than 25% of stimulation pulses were affected by clipping.