The overtone spectra of adamantane, 1-chloroadamantane, and hexamethylenetetramine have been recorded in various phases and at several temperatures. Phase effects and temperature effects on the overtone spectra are discussed. The vibrational overtone spectra are recorded by conventional near-infrared spectroscopy and by intracavity laser photoacoustic spectroscopy. Peaks corresponding to the nonequivalent CH oscillators of adamantane vapor and 1-chloroadamantane vapor are assigned. Absolute oscillator strengths of adamantane are determined from the conventional spectra, and they are compared with values calculated with a harmonically coupled anharmonic oscillator local mode model and ab initio dipole moment functions. Very good agreement between observed and calculated intensities is obtained.