  The {\sc Majorana Demonstrator will search for the neutrinoless double-beta
decay of the isotope Ge-76 with a mixed array of enriched and natural germanium
detectors. The observation of this rare decay would indicate the neutrino is
its own antiparticle, demonstrate that lepton number is not conserved, and
provide information on the absolute mass scale of the neutrino. The {\sc
Demonstrator} is being assembled at the 4850-foot level of the Sanford
Underground Research Facility in Lead, South Dakota. The array will be situated
in a low-background environment and surrounded by passive and active shielding.
Here we describe the science goals of the {\sc Demonstrator} and the details of
its design.
