Hearing loss causes difficulties in maintaining access to and understanding of spoken language; it is often thought of as a simple loss of audibility of sound, which is only partially true. Hearing aids amplify sounds in a frequency-specific manner, restoring audibility but only to a point. The more challenging aspect of hearing loss is sound distortion, including frequency smearing. When hearing aids cannot provide sufficient benefit, individuals should consider cochlear implantation. CIs bypass the damaged structures of the inner ear and provide access to speech information via direct electrical stimulation of the neural elements of the auditory system, providing loudness and clarity when hearing aids cannot. Due to neural plasticity, which is promoted through training and rehabilitation, the brain can often use the novel electrical signal to result in good outcomes. Originally, CIs were designed as tools to improve speech understanding in quiet environments. Most individuals who undergo cochlear implantation end up hearing better than they did with their hearing aids. Now, after advancements in technology and methods, CI users are demonstrating improvements in hearing during most listening situations; some are even enjoying music again. There is a range of variability in outcomes, mostly due to the duration of deafness, time to implantation, and postoperative rehabilitation. Looking back over 40 years, the developments in CI technology, programming, and rehabilitation have been substantial. The next 40 years will hopefully bring further advances. This may include better coordination across ears to improve spatial-hearing outcomes and auditory-grouping abilities; sound-processing strategies that help to better convey pitch and music by providing usable temporal fine structure and harmonic structures; perhaps using infrared light to stimulate the cochlea; and novel forms of electrical stimulation like auditory nerve implants.