The size of certain brain parts involved in the processing of auditory stimuli was measured in European wild boars (Sus scrofa) and domestic pigs (Sus scrofa f. dom.). By means of intraspecific allometric methods for analyzing the brain weight to body weight relationships, the volumes were compared in both groups. In general, all measured structures were smaller in the domestic form, indicating that domestication has led to a decrease in the size of auditory brain parts. Within the auditory system, however, differences in the amount of decrease were observed in different structures. The cochlear nucleus is only 15% smaller and the medial geniculate body about 20% smaller in the domestic form, whereas the superior olive (28%), the inferior colliculus (28%), the grey matter of the auditory cortex (32%) and the lateral lemniscus (33%) are decreased more significantly. Furthermore, in the medial superior olivary nucleus, there are 9% fewer neurons in the domestic form, but the neuron density has increased by 28%.