The star formation history and the compositions of stellar generations, the
present as well as past ones, are closely coupled to the nature of the
interstellar medium (ISM). In particular, the molecular component of the
ISM is important since it contains the main birth-sites of stars. The
Magellanic Clouds are excellent targets for studying the rôle of the
environment in the formation and the evolution of molecular clouds and
stars. Therefore a major study of different molecular species, including
isotopic variants, have been performed in selected regions of the SMC and
LMC. Molecular abundances have been estimated, and found to be
significantly lower in the LMC than in the Galaxy, and even more so in the
SMC. This is an effect of both the lower metallicity and the higher
interstellar UV radiation field in some regions. The C 
O/C 
O
ratio have been used to study the star formation history in the LMC.
Global maps of the distribution of the molecular medium in external
galaxies are very rare. A significant contribution to this area is a
CO(1-0) mapping project of the southern, barred, grand-design spiral galaxy
M83. The galaxy is inclined so that both distribution and kinematical
studies can be performed. About 6 
8 arcminutes have now been
covered.