  The first definite discoveries of extragalactic deuterium are reported.
DCO$^+$ has been detected in three and DCN has been measured in one
star-forming region of the Large Magellanic Cloud (LMC). While the
HCO$^+$/DCO$^+$ abundance ratios are found to be 19 $\pm$ 3, 24 $\pm$ 4, and 67
$\pm$ 18 for N113, N44BC and N159HW, respectively, a HCN/DCN abundance ratio of
23 $\pm$ 5 is obtained for N113. These results are consistent with a gas
temperature of about 20\,K and a D/H ratio of about $1.5 \times 10^{-5}$,
consistent with that observed in the Galaxy. If the cloud temperature is closer
to 30\,K, then a D/H ratio is required to be up to an order of magnitude
larger. Because this ratio provides a lower limit to the primordial D/H ratio,
it indicates that the baryon mass density alone is unable to close the
universe.
