Deuterium chemistry in protoplanetary disks
          Karen Willacy
          Bill Langer
          Geoff Bryden

          Observations of deuterated molecules can give important information about the physical conditions under which they were formed.  Recent observations of deuterated molecules in protoplanetary disks have shown that the D/H ratio is high, similar to that seen in prestellar cores.  We present the results of models of the deuterium chemistry in cores and discuss whether observations can be used to distinguish between different disk models.