The first detection of interstellar DNC has been obtained in the J = 2-1 line in the sources NGC 1333, Ori A, NGC 2264, and in the dark cloud L134. An HN(C-13)/DNC abundance ratio of no more than 3.2 is found in NGC 2264, indicating substantial deuterium enhancement. An even larger enhancement is indicated in L134. Proposed fractionation chemistries can account for such enhanced ratios in regions of low temperature. The variation in the HNC/DNC abundance ratio may be a stronger function of physical conditions in clouds than of the D/H abundance ratio.