New infrared data are reported for disilylmethane-d(0) and -d(6) in the gas phase. Quantum-chemical (QC) calculations have been carried out at HF, MP2, and B3LYP levels with a variety of basis sets. These verify the previously obtained experimental C-2v structure. The two possible kinds of SiH bonds are identical in strength but not in electrical properties. Reassignments are made of several vibration frequencies. The A(2) and B-2 torsional frequencies are estimated to be 78.5 and 133 cm(-1), respectively, from combination and difference bands. QC-based force fields scaled with 14 factors are used to predict unknown or uncertain frequencies. Scale factors for the A2 torsion are highly variable with level and basis. By contrast, similar QC calculations of torsional frequencies in disilane, methyl-, fluoro-, chloro-, and ethyl-silanes show very little variation. Stretch/stretch interaction constants between SiH bonds in different silyl groups correlate well with the dipole-dipole energies derived from the QC calculations. Electrical properties of the SiH bond are compared across a range of SiH-containing compounds. A survey of CH stretch/CH stretch interaction force constants in 17 molecules containing CH3 or CH2 groups indicates that MP2 calculations are unlikely to be suitable for close analyses of the stretching frequencies of these groups.