Recently, there are a few reports on the life expectancy after head injury. Estimation of the expected life span of a certain disabled persons after head injury is neither simple nor easy. However, the expert should report the most probable scientific estimates. The author had reviewed literatures on the life expectancy of head injured persons, and proposed a scheme for estimation of the life expectancy of disabled persons after head injury. The expert should be aware of the basic scheme and the most updated literature. For the best estimates, the expert should assess the degree of disability and health status in detail and analyze the scientific data on the length of survival for such patients logically.