Objective: To study the importance of neural response telemetry and its diagnostic value and to compare Electrically Evoked Compound Action Potential (ECAP) with Map thresholds (T-level) and maximum comfort (C-levels) for adults and children.Research Design and Methods: Clinical examination (otological, audiological), transient evoked otoacoustic emission, brain stem audiometry, procedure for stimulation and recording of the ECAP, behavioral measures, speech recognition testing for the following subjects: Twenty two patients (10 adults and 12 children) implanted with Nucleus CI24M cochlear implant at the Cochlear Implant Unit-Cairo University.Results: ECAP growth function measures were positively correlated to Map T and C levels, but non of the ECAP measures were significantly correlated to postoperative speech discrimination. Using a gain of 60dB gave more reliable results.Conclusion: ECAP growth function measures are useful tools in assisting the prediction of behavioral maps, using a gain of 60dB gives more reliable responses.