  We present high spectral-resolution optical spectra of 49 Herbig Ae/Be stars
in a search for the [O I] 6300A line. The vast majority of the stars in our
sample show narrow (FWHM < 100 km/s) emission lines, centered on the stellar
radial velocity. In only three sources is the feature much broader (~400 km/s),
and strongly blueshifted (-200 km/s) compared to the stellar radial velocity.
Some stars in our sample show double-peaked lines profiles, with peak-to-peak
separations of ~10 km/s. The presence and strength of the [O I] line emission
appears to be correlated with the far-infrared energy distribution of each
source: stars with a strong excess at 60 micron have in general stronger [O I]
emission than stars with weaker 60 micron excesses. We interpret these narrow
[O I] 6300A line profiles as arising in the surface layers of the
protoplanetary disks surrounding Herbig Ae/Be stars. A simple model for [O I]
6300A line emission due to the photodissociation of OH molecules shows that our
results are in quantitative agreement with that expected from the emission of a
flared disk if the fractional OH abundance is ~5 x 10^{-7}.
