  A study of the gas content in 1038 interacting galaxies, essentially selected
from Arp, Arp and Madore, Vorontsov-Velyaminov catalogues and some of the
published literature, is presented here. The data on the interstellar medium
have been extracted from a number of sources in the literature and compared
with a sample of 1916 normal galaxies. The mean values for each of the
different ISM tracers (FIR, 21 cm, CO lines, X-ray) have been estimated by
means of survival analysis techniques, in order to take into account the
presence of upper limits. From the data it appears that interacting galaxies
have a higher gas content than normal ones. Galaxies classified as ellipticals
have both a dust and gas content one order of magnitude higher than normal.
Spirals have in most part a normal dust and HI content but an higher molecular
gas mass. The X-ray luminosity also appears higher than that of normal galaxies
of same morphological type, both including or excluding AGNs. We considered the
alternative possibilities that the molecular gas excess may derive from the
existence of tidal torques which produce gas infall from the surrounding
regions or from a different metallicity which affects the X conversion factor
between the observed CO line luminosity and the H$_2$ calculated mass.
According to our tests, it appears that interacting galaxies possess a higher
molecular mass than normal galaxies but with a similar star formation
efficiency.
