Mismatch negativity (MMN) provides an objective measure for evaluating subjects with problems related to speech processing. For a valid neurophysiological profile of speech-processing mechanisms, an efficient procedure to elicit MMNs is needed. In Experiment 1 of this study, MMN recordings were conducted in adults with normal hearing on the effects of decreasing the duration of the interstimulus interval (ISI). Shortening ISI duration does not seem to have a high impact on the individual MMN quality, whereas it does influence group MMN quality. In Experiment 2, MMNs were elicited in a group of cochlear implant users by using a speech sound contrast /bα/-/dα/. A group of good performers produced a signifycant MMN, whereas a group of moderate performers did not. There seems to be a relation between speech perception ability and MMN quality. To fundamentally understand the effects of electrical stimulation of the inner ear and to clinically adjust rehabilitation, diverse data are needed on different aspects of auditory processing. Optimizing the procedure to elicit and MMN is therefore of great clinical value.