Behavioural responses have been elicited to acoustic stimuli in hereditarily deaf white mink (Hedlund). This revealed onset of auditory function at an average age of 31 days. The period of hearing lasted on the average only 7 days. Similar observations have been reported in other hereditarily deaf animals (cat, mouse, guinea pig). It is suggested that the onset of auditory function follows a progressive pattern which corresponds to the circulation of blood in the cochlea. Moreover, it is suggested that the subsequent deterioration of hearing follows a regression of this vascular pattern and thus a vascular pathogenesis may be responsible for this type of genetic deafness.