High resolution Fourier transform infrared emission spectra of MgH and MgD have been recorded. The molecules were generated in an emission source that combines an electrical discharge with a high temperature furnace. Several vibration-rotation bands were observed for all six isotopomers in the X (2)Sigma(+) ground electronic state: v=1-->0 to 4-->3 for (MgH)-Mg-24, v=1-->0 to 3-->2 for (MgH)-Mg-25 and (MgH)-Mg-26, v=1-->0 to 5-->4 for (MgD)-Mg-24, v=1-->0 to 4-->3 for (MgD)-Mg-25 and (MgD)-Mg-26. The new data were combined with the previous ground state data, obtained from diode laser vibration-rotation measurements and pure rotation spectra, and spectroscopic constants were determined for the v=0 to 4 levels of (MgH)-Mg-24 and the v=0 to 5 levels of (MgD)-Mg-24. In addition, Dunham constants and Born-Oppenheimer breakdown correction parameters were obtained in a combined fit of the six isotopomers. The equilibrium vibrational constants (omega(e)) for (MgH)-Mg-24 and (MgD)-Mg-24 were found to be 1492.776(7) cm(-1) and 1077.298(5) cm(-1), respectively, while the equilibrium rotational constants (B-e) are 5.825 523(8) cm(-1) and 3.034 344(4) cm(-1). The associated equilibrium bond distances (r(e)) were determined to be 1.729 721(1) A for (MgH)-Mg-24 and 1.729 157(1) A for (MgD)-Mg-24. (C) 2004 American Institute of Physics.