We describe the decoherence-free subspace of N atoms in a cavity, in which
decoherence due to the leakage of photons through the cavity mirrors is sup
pressed. We show how the states of the subspace can be entangled with the h
elp of weak laser pulses, using the high decay rate of the cavity field and
strong coupling between the atoms and the resonator mode. The atoms remain
decoherence-free with a probability which can, in principle, be arbitraril
y close to unity.