Structures of (aniline-benzene)(+) and (aniline)(2)(+) are re-investigated by electronic spectroscopy in the near-infrared region and vibrational spectroscopy in the NH stretching region. The spectra of (aniline-benzene)(+) indicate a structure including a hydrogen bond between an NH bond of the ionic aniline and the pi-electrons of the neutral benzene. Two isomers are suggested for (aniline)(2)(+) in which an NH bond of the ionic aniline forms different types of hydrogen bond with the neutral aniline: one with the pi-electrons of the aromatic ring and the other with the lone pair of the nitrogen atom. (C) 2000 Elsevier Science B.V. All rights reserved.