The Answer:

Of those countries for which the U.S. Bureau of the Census provides statistics, Japan has the longest average life expectancy, at 81.2 years, as of 2005. The shortest is found in Angola, at 36.6. This doesn't account for countries not listed, though.

It also should be noted that Angola's 36.6 year life expectancy doesn't mean that a 35-year-old there is likely to die within two years. The number is an average, pulled way down by a high infant mortality rate. Close to one out of every five Angolan children dies in infancy.

—The Fact Monster