In these lectures I describe the remarkable ultraviolet behavior of N=8
supergravity, which through four loops is no worse than that of N=4
super-Yang-Mills theory (a finite theory). I also explain the computational
tools that allow multi-loop amplitudes to be evaluated in this theory - the KLT
relations and the unitarity method - and sketch how ultraviolet divergences are
extracted from the amplitudes.Comment: 30 pages, 12 figures; lectures presented at International School of
Subnuclear Physics, 47th Course, Erice Sicily, August 29-September 7, 200