Infrared and photoluminescence spectra of matrix-isolated and thin-film samples (both at 11 K) of tris(8-hydroxyquinolinato)aluminum(III) (Alq(3)) and tris(4-methyl-8-hydroxyquinolinato)aluminum (Almq(3)) were collected and compared to vibrational spectra generated by B3LYP based density functional calculations. The present infrared spectral results suggest that both Alq(3) and Almq(3) exist primarily in the meridional or C-1 isomeric form with little or no spectral evidence for the presence of the alternate, facial (C-3 symmetry) geometric isomer. In addition, photoluminescence spectra of these molecules isolated in an argon matrix show vibronic structure in the emission band associated with the S-1 --> S-0 transition.