Evidence from surface tension, sum frequency, and molecular scattering measurements in other laboratories has suggested that molecular HNO3 is present at the surface of concentrated binary HNO3-H2O and ternary HNO3-H2SO4-H2O solutions. We report here direct infrared spectroscopic evidence for the presence of HNO3 at the air interface with both types of solutions at room temperature. Both attenuated total reflectance (ATR) and single reflectance SR-FTIR were applied to HNO3-H2O solutions ranging from 0.9 to 40 mol % (0.5-15.7 M) and to ternary. solutions containing a constant amount of H2SO4 (25 mol %) and increasing concentrations of nitric acid from 0 to 25 mol % and associated decreasing amounts of water from 75 to 50 mol %. ATR spectra are analogous to transmission spectra, while SR spectra are more sensitive to species at or near the air interface where reflection occurs. Comparison of the ATR and SR spectra of the most concentrated solutions clearly show molecular HNO3 at or near the surface. Furthermore, the spectra suggest that for these more concentrated solutions, the major form of nitric acid in the HNO3-H2O solution is the monohydrate, HNO3 H2O, while in the H2SO4-HNO3-H2O solution, it is the anhydrous form. The potential atmospheric implications are discussed.