The author discusses cholesteatomas of the choroid plexus of the lateral ventricles of the cerebrum and of the base of the cerebellum in Equidae, examining some aspects of aetiology of this cholesteatosis based on the literature and on his personal observations. He describes for the first time in Brazil, cases of cholesteatomas in Equidae, 14 in number of a total of 38 solipeds examined (36,8%). He found the presence of the lesion in the mule: a fact not yet men¬tioned in the literature.