  We study the spectral properties in the range 3600 \AA - 6800 \AA of the
nuclear region of galaxies behind the Magellanic Clouds. The radial velocities
clarified the nature of the objects as background galaxies or extended objects
belonging to the Clouds. For most galaxies behind the main bodies of the LMC
and SMC, radial velocities were measured for the first time. In the present
sample typical LMC background galaxies are nearby (4000 < V(km/s) < 6000),
while SMC's are considerably more distant (10000 < V(km/s) < 20000). We
determine the reddening in each line of sight by matching a reddening-free
galaxy template with comparable stellar population. For the LMC main body we
derive a combined Milky Way and internal reddening value E(B-V)$_{MW+i}$ =
0.12$\pm$0.10, while for the SMC E(B-V)$_{MW+i}$ = 0.05$\pm$0.05. By
subtracting Milky Way reddening values for galaxies projected onto the
surroundings of each Cloud, we estimate average internal reddening values
$\Delta$E(B-V)$_i$ = 0.06 and 0.04, respectively for the main bodies of the LMC
and SMC. The Clouds are optically thin, at least in the directions of the
studied background galaxies which are often difficult to be identified as such
on ESO/SERC sky survey images. Nevertheless, more reddened zones may occur
where it is difficult to identify galaxies.
