A novel technique of saturation spectroscopy is applied to study the individual vibronic spectra of single impurity molecules embedded in a low-temperature solid matrix, Homogeneous linewidths and vibrational frequencies for two lower vibronic levels of the excited electronic state S-1 are determined for several terrylene single molecules in a naphthalene crystal, which indicates a noticeable distribution of these parameters. A certain correlation can be pointed out between vibrational frequency and a purely electronic transition frequency of a terrylene molecule. (C) 2002 Elsevier Science B.V. All rights reserved.