Since its discovery by IRAS, the uniqueness and evolutionary state of
 the beta Pictoris disk have been topics of lively discussion. While
 detailed studies of beta Pic have revealed the presence of a cleared inner
 region, with implications for planet formation, and the presence of
 accreting gas tentatively associated with comet-like bodies, observations
 of other systems, particularly  younger ones, are needed to obtain a better
 understanding of the evolutionary history of the  beta Pic system.
 During the past 2 years we have identified a number of PMS Herbig Ae/Be stars
 which are viewed through a significant portion of their circumstellar dust
 disks, and which exhibit accreting gas similar to, but higher in accretion
 rate than beta Pic.  The available data suggest a correlation between the
 signatures of mass accretion, the prominence of optical indicators of dust
 in close proximity to the star, mass return to the ISM, and the shape of the
 IR spectral energy distribution.  The spectroscopy suggests that signatures
 of accreting volatile gases disappear prior to the refractory species.  The
 optical/UV data give no information on volatile molecules or ices, and thus
 do not sample the species which are most characteristic of a proto-planetary
 disk in its earliest evolutionary phases. The time scale for volatile depletion
 is a critical parameter in planetary formation models, and constrains
 the mass of any gas giant which can be formed in a planetary system.
 The mid-IR spectrum, as sampled by the ISO SWS, is rich in bands from
 volatile molecules which are expected to be abundant in proto-planetary disks,
 PAH features, sampling small organic grains, silicate bands sampling the
 refractory grains which are expected to be most important close to the stars,
 and ice features. Acquisition of a homogeneous sample of low resolution spectra
 for a group of Herbig Ae/Be stars chosen to span a range in age and degree of
 central clearing, together with a range in spectral type will permit us to
 constrain the time available for gas giant formation, and hence the expected
 planetary masses, more stringently than current estimates which are based
 on the disappearance of the dust disk.