Electrophysiological investigations, at different levels of the auditory pathway, were performed on 54 white cats. Hearing tests generally consisted of recording electrocochleograms or making audiograms from collicular or cortical responses. Some investigations were performed with chronically implanted electrodes to detect the first appearance of a hearing defect. Results showed no evident relationship between the age of the white cat and the appearance, severity or completeness of hearing loss. A large variety of hearing remnants was encountered in partly deaf animals which is tentatively related to a similar variety of histological damage of the cochlea described in a companion paper (Rebillard, M., Pujol, R. and Rebillard, G. (1981): Hearing Res. 5, 189-200).