Studies to elucidate changes in the contents of ulinastatin-like immunoreactive substance (UTIRS) and α1 -microglobulin-like immunoreactive substance (α1MIRS) in cerebrospinal fluid (CSF) of patients with dementia were performed. Levels of UTIRS in the dementia group were significantly (p < 0.01) lower than those in dementia-free subjects. In addition, lower levels of UTIRS were registered in subjects afflicted with a higher severity of dementia. However, the levels of αlMIRS were not affected in the dementia group compared with dementia-free subjects. Neither UTIRS nor α1MIRS contents were related to the existence and stages of Parkinson’s disease. These results suggest that UTIRS levels in the CSF are associated with the severity of dem