The purpose of this paper is to show several diseases that manifest symmetrical hyperintense lesions on the middle cerebellar peduncles, the largest connecting peduncles between the brainstem and the cerebellum, in conventional magnetic resonance (MR) images. We retrospectively reviewed cranial MR images obtained with 0.3-, 0.5-, 1.0-, and 1.5-Tesla scanners. We found symmetrical middle cerebellar peduncular lesions in patients with Wilson's disease; hepatic encephalopathy; extrapontine myelinolysis; acute disseminated encephalomyelitis; wallerian degeneration of the pontocerebellar tracts after either pontine infarction, pontine hemorrhage, or central pontine myelinolysis; leukodystrophy; olivopontocerebellar atrophy; and toluene abuse. Definitive diagnosis of these diseases can be made relatively easily on the basis of clinical data; however, examination of associated brainstem or supratentorial lesions in MR images is also important.