Cochlear implants are increasingly used in the rehabilitation of the profoundly and totally deaf. Usually, insufficient gain of speech discrimination with a powerful conventional hearing aid is considered as a prerequisite for a cochlear prosthesis. With recent improvements of electronic systems, the criterion for this decision may change. To keep pace with the technical progress, a battery of speech sound tests suited for minimal auditory capabilities (MAC-battery) was developed and applied to groups of patients fitted with conventional instruments and with two different types of cochlear implants. Based on the comparison of the MAC-battery results of hearing aid groups, with the average performance of an implanted group, most conventionally fitted regular users of hearing aids should not be considered as candidates for cochlear implantation. The MAC-battery, although not a strictly standardized procedure, is a useful instrument for patient counselling and for the selection of implant candidates.