An autosomal-dominant progressive hereditary sensorineural hearing loss with onset in the high frequencies was studied in a Dutch family with 105 affected individuals. The hearing loss was analyzed by a curve-fitting procedure. A hyperbolic tangent was fitted into the audiogram. Five characteristics were distinguished: the high-frequency plateau, the low-frequency plateau, the slope, the low cut-off frequency and the high cut-off frequency. Six phases are recognizable in the development of the hearing loss, which is characterized by a two-step progression, first in the high and then in the low frequencies. Great differences in the rate of the deterioration were observed. The age of onset is between 5 and 15 years.