The health insurance system in Japan is compared to the U.S. system from a neurosurgeon's perspective. The Japanese entire population is enrolled in mandatory health insurance without choice based on employment and residence, called “Health-insurance-for-all.” Elderly Health Insurance for senior people aged 70 years or older is set within each health organization. As the relative financial conditions are variable among health insurance organizations, financial adjustment is done. The medical fee is set for all the procedures and products that are paid by health insurance which sets the prices. The same fee schedule applies to both private-practice physicians and hospitals. In the U.S. system, there are numerous fee schedules including both doctor fees and hospital fees. Any extra charges (balance billing) for procedures or materials that are not listed in the fee schedule are strictly prohibited. There is an escape clause that is called the specified medical fee system (“Tokutei Ryoyohi” in Japanese). Some designated items can be exceptionally paid by health insurance fee schedule. Many Japanese neurosurgeons express dissatisfaction with the lack of approval for medical materials which have already been used safely in other countries. The retrospective claim review process includes intermediaries, quasi-public organizations that act as payment makers to providers and claim review boards. Peer-review boards consist of about 8,000 physicians. The billing process itself using the same, uniform fee schedule is very uncomplicated, and has helped to diminish the need for well-trained and well-paid managers, and controlled administrative costs in Japan. Most medical expenses were consumed by a few patients who underwent high-cost medical care. Medical expenditure for the elderly is already taking 1/3 of national health expenditure, and is projected to reach 1/2 of national health expenditure by the year 2025. There is catastrophic coverage for high-cost care or a cap on monthly co-payment spending (High-Priced Medical Fee system: Kogaku Ryoyohi Seido). To maintain reliable and stable medical insurance systems in the aging society with fewer children in the 21st century, it is essential that fundamental reform is introduced across all systems.