  Based on two models, we investigate the molecular-to-atomic gas ratio in
Virgo cluster galaxies in comparison with field galaxies. We show that the
enhanced metallicity for cluster members and the ram pressure stripping of
atomic gas from the disk periphery cannot fully explain the observed gas
component ratios. The additional environmental factors affecting the
interstellar medium and leading to an increase in the molecular gas fraction
should be taken into account for cluster galaxies.
