  To test the PDR model spectra under the physical conditions present in Orion,
we have obtained moderate-resolution (R=3000) J-, H-, and K-band long-slit
spectra of the Orion bar and Orion S regions These observations provide
conclusive evidence for the PDR origin (rather than shocks) of the H_2 emission
in each of these regions and demonstrate significant departures in the observed
chemical structure from that predicted by models of homogeneous PDRs.
