A detailed analysis of the high-resolution infrared emission spectra of gaseous HgH2 and HgD2 in the 1200212 2200 cm(-1) spectral range is presented. The nu(3) antisymmetric stretching fundamental bands of (HgH2)-Hg-204, (HgH2)-Hg-202, (HgH2)-Hg-201, (HgH2)-Hg-200, (HgH2)-Hg-199, (HgH2)-Hg-198, (HgD2)-Hg-204, (HgD2)-Hg-202, (HgD2)-Hg-201, (HgD2)-Hg-200, (HgD2)-Hg-199, and (HgD2)-Hg-198, as well as a few hot bands involving nu(1), nu(2), and nu(3) were analyzed rotationally, and spectroscopic constants were obtained. Using the rotational constants of the 000, 100, 0 110, and 001 vibrational levels, we determined the equilibrium rotational constants (B-e) of the most abundant isotopologues, (HgH2)-Hg-202 and (HgD2)-Hg-202, to be 3.135325(24) cm(-1) and 1.569037(16) cm(-1), respectively, and the associated equilibrium Hg-H and Hg-D internuclear distances (r(e)) are 1.63324(1) angstrom and 1.63315(1) angstrom, respectively. The r(e) distances of (HgH2)-Hg-202 and (HgD2)-Hg-202 differ by about 0.005%, which can be attributed to the breakdown of the Born-Oppenheimer approximation.