The epidemiological aspect of chronic subdural hematoma (CSH) in the elderly who are 65 years old or elder was evaluated on Awaji Island with about 170,000 inhabitants. The overall incidence of CSH was 13.1 per 100,000/year, 3.4 in people under 65 years old, and 58.1 in the elderly. The elderly were 17.7% of all inhabitants. If these incidences of CSH are extrapolated to all of Japan in the year 2020, the incidence will be 16.3 per 100,000/year. This suggests that CSH may become the most common neurosurgical condition.