We prove for any pure three-quantum-bit state the existence of local bases
which allow one to build a set of five orthogonal product states in terms o
f which the state can be written in a unique form. This leads to a canonica
l form which generalizes the two-quantum-bit Schmidt decomposition. It is u
niquely characterized by the five entanglement parameters. It leads to a co
mplete classification of the three-quantum-bit states. It shows that the ri
ght outcome of an adequate local measurement always erases all entanglement
between the other two parties.