  We present a scheme for probabilistic teleportation via a non-maximally
entangled GHZ state. Quantum teleportation will succeed with a certain
probability if the sender makes a generalized Bell state measurement, the
cooperator performs a generalized $X$ basis measurement, and the receiver
introduces an auxiliary particle, performs a collective unitary transformation
and makes a measurement on the auxiliary particle. The success probability of
the teleportation is given. We also obtain the maximum of the success
probability of the teleportation.
