  We report the results of coincidence counting experiments at the output of a
Michelson interferometer using the zero-phonon-line emission of a single
molecule at $1.4 K$. Under continuous wave excitation, we observe the absence
of coincidence counts as an indication of two-photon interference. This
corresponds to the observation of Hong-Ou-Mandel correlations and proves the
suitability of the zero-phonon-line emission of single molecules for
applications in linear optics quantum computation.
