  Nine HII regions of the LMC were mapped in 13CO(1--0) and three in 12CO(1--0)
to study the physical properties of the interstellar medium in the Magellanic
Clouds. For N113 the molecular core is found to have a peak position which
differs from that of the associated HII region by 20 arcsec. Toward this
molecular core the 12CO and 13CO peak Tmb line temperatures of 7.3\,K and
1.2\,K are the highest so far found in the Magellanic Clouds. The molecular
concentrations associated with N113, N44BC, N159HW, and N214DE in the LMC and
LIRS\,36 in the SMC were investigated in a variety of molecular species to
study the chemical properties of the interstellar medium. $I$(HCO+)/$I$(HCN)
and $I$(HCN)/$I$(HNC) intensity ratios as well as lower limits to the
$I$(13CO)/$I$(C18O) ratio were derived for the rotational 1--0 transitions.
Generally, HCO+ is stronger than HCN, and HCN is stronger than HNC. The high
relative HCO+ intensities are consistent with a high ionization flux from
supernovae remnants and young stars, possibly coupled with a large extent of
the HCO+ emission region. The bulk of the HCN arises from relatively compact
dense cloud cores. Warm or shocked gas enhances HCN relative to HNC. From
chemical model calculations it is predicted that $I$(HCN)/$I$(HNC) close to one
should be obtained with higher angular resolution ($>$ 30 arcsec) toward the
cloud cores. Comparing virial masses with those obtained from the integrated CO
intensity provides an H2 mass-to-CO luminosity conversion factor of $1.8 \times
10^{20}$\,mol\,cm$^{-2}$\,(Kkms)$^{-1}$ for N113 and $2.4 \times
10^{20}$\,mol\,cm$^{-2}$\,(Kkms)$^{-1}$ for N44BC. This is consistent with
values derived for the Galactic disk.
