  Recently Eibl et al. [PRL 92, 077901 (2004)] reported the experimental
observation of the three-photon polarization-entangled W state. In this Comment
we point out that, actually, the particular measurements involved in the
experiment testing Mermin's inequality cannot be used for the verification of
the existence of genuinely quantal tripartite correlations in the observed
state, and therefore this state cannot conclusively be identified with the W
state.
