Background: Little is known about the side effects of sedative-hypnotic agents in elderly dementia patients with sleep disorders. The present study describes activity pattern changes after a single dose of brotizolam in elderly patients with dementia. Methods: We conducted retrospective analysis of prospectively collected data from a case series at Asakayama Hospital (Osaka, Japan) between September 2008 and September 2009. Around-the-clock movements of dementia patients who were administered a single dose of brotizolam were recorded by the integrated circuit tag monitoring system during a 4-week baseline and 7-day peri-administration period. Diurnal and nocturnal activity levels and the onset times of the least-active and most-active phases were then measured. Results: Seven patients (four men, three women; age range 5985 years) were analyzed. All seven patients had disturbed activity patterns during the peri-administration period. Compared with the pre-administration period, the incidence of reversed rest-activity pattern increased significantly in the post-administration period, as measured by the distance moved per hour (P < 0.000). Patients with advanced stages of dementia had prolonged and delayed activity responses. Conclusions: Findings showed changes in activity levels and reversed active/resting phases after a single dose of brotizolam in elderly patients with dementia. Use of brotizolam in elderly patients with dementia, especially in advanced stages, calls for closer attention and longer observation periods.