Spectroscopic information of ternary aniline clusters which include water has been obtained for the first time by infrared depletion spectroscopy. The vibrational spectra of the NH and OH stretching region of aniline-water-tetrahydrofuran (THF) clusters and their cations were measured by using infrared (IR) depletion spectroscopy. The infrared spectrum of the neutral cluster showed four absorption bands at 3715 cm(-1) (free OH), 3491 cm(-1) (free NH), 3403 cm(-1) (bonded OH), and 3376 cm(-1) (bonded NH). Analysis of the frequency red shifts of these bands showed that this cluster has a chainlike structure; the NH bond of aniline interacts with the oxygen atom of water, and one OH group of water interacts with the oxygen atom of THF. In contrast, the aniline cation acted as a double donor of hydrogen in the cluster cation. The infrared spectrum of the cluster cation showed three absorption bands at 3722 cm(-1) (antisymmetric stretching of OH). 3636 cm(-1) (symmetric stretching of OH), and 3230 cm(-1) (bonded NH). Analysis of the red shifts of the infrared bands showed that the main interactions were the hydrogen bond between the NH bond of aniline and the oxygen atom of THF and that between the NH bonds of aniline and the oxygen atom of water.