The authors studied 23 patients with cerebellar degeneration including multiple systemic atrophy (MSA) and cerebellar cortical atrophy (CCA) by proton magnetic resonance spectroscopy (1H-MRS). 1H-MRS allowed noninvasive measurement of the signal intensities derived from N-acetylaspartate (NAA), creatine + phosphocreatine (CRE), and choline-containing compounds (CHO). There was significant reduction of the NAA/CRE level in the frontal cortex, putamen, cerebellar hemisphere and cerebellar vermis of patients with MSA, and in the frontal cortex, cerebellar hemisphere and cerebellar vermis of patients with CCA as compared with those of normal controls. There was significant reduction of the NAA/CRE level also in the putamen of patients with MSA as compared with that of patients with CCA. These results indicated the presence of a degenerative process and/or functional impairment in the frontal cortex and putamen of patients with MSA and in the frontal cortex of patients with CCA, in addition to a degenerative process in the cerebellum. There was a significant correlation between the NAA/CRE level and the severity of clinical signs. 1H-MRS is valuable in providing information regarding the pathophysiology and the progress of cerebellar degenerative diseases.