We have observed several IR bands of CH3CN-BF3 in neon and nitrogen matrices. For the B-11 isotopomer in neon matrices, we observed the BF3 symmetric deformation band (nu(7)) as a doublet at 600 and 603 cm(-1), the BF3 symmetric stretching band (nu(6)) as a doublet at 833 and 838 cm(-1), the BF3 asymmetric stretching mode (nu(13)) at 1281 cm(-1) (partially obscured), and the C-N stretching mode (nu(2)) as a doublet at 2352 and 2356 cm(-1). The nitrogen matrix data are largely consistent with those reported recently, though we do propose a refinement of one band assignment. Comparisons of the frequencies of a few key, structurally sensitive vibrational modes either observed in various condensed-phase environments or calculated for two minimum-energy gas-phase structures indicate that inert matrix media significantly alter the structural properties of CH3CN-BF3. Specifically, the B-N dative bond compresses relative to the gas phase and other concomitant changes occur as well. Furthermore, the frequency shifts depict structural changes that occur across the various matrix hosts in a manner that largely parallels the degree of stabilization offered by these inert media.