In a few introductory remarks the technological, neurophysiological and clinical assessments of new developments in modern, highly sophisticated hearing aids are reviewed. The necessity of preprocessing auditory information is discussed as well as the problems related to the choice of suitable electrodes, and, in particular, how much auditory information for speech communication, given by the product of number of just noticeable differences in intensity, number of just noticeable differences in frequency, number of channels for conveying neurophysiologically processable signals would be required as a minimum for cochlear implants to enable patients to communicate with one another. Finally, the fact that a number of different sensory modalities converge in to man's cortical association area might possibly be used for some special application of a multimodal input in a completely deaf patient with the aim of enabling him to understand human speech.