Infrared absorption spectra of aniline, trapped in a low-temperature 5 K argon matrix, have been obtained in the spectral region from 500 to 4000 cm(-1). The aniline cation C6H7N+, was formed inside the matrix by UV laser irradiation. We report the first IR absorption spectroscopy of this cation in an argon matrix: five fundamental vibrational bands were observed.