Cen A is the nearest active galaxy. At radio frequencies it appears
as an extended and very strong source, with a VLBI-core, a one-sided jet,
Double Inner Lobes, a Northern Middle Lobe and two Giant Outer Lobes (see
Ebneter & Balick 1983 for details). The large-scale radio structure has
been studied by several authors: Cooper et al.
(1965), Haynes et al. (1983),
and recently Junkes et al. (1993). The latter have presented results of a
6.3 cm continuum and polarization survey of the whole source
obtained with the Parkes radiotelescope. Their work will be completed by
similar radio observations at 
3 cm whose analysis will provide
information about the spectral index distribution, rotation measures and
depolarization. Here we present some complementary data to these studies.
By means of the 408 MHz continuum observations carried out by Haslam et
al. (1981) and new 1435 MHz observations we have computed a spectral index
map of the extended source. This map, together with the polarization maps
presented by Junkes and co-workers, can provide valuable information
about the physical processes occurring in the large-scale structure of Cen
A. Previous computations of the spectral indices of the extended radio
emission in this source were restricted to
mean values (Cooper et al. 1965).