Tadeusz Wasiutyński wrote on 05/07/2011 07:32 AM:
 > Hello,
 > do I need rpmbuild? I do not see it in my SL6.
 > Regards
 > Tadeusz

Tadeusz,

Please reply to the list.  I wish that were the default, as is seems to 
be with most other lists I use.

To your question:

$ which rpmbuild
/usr/bin/rpmbuild
$ rpm -qf /usr/bin/rpmbuild
rpm-build-4.8.0-12.el6.i686

You could also do:
# yum provides \*/rpmbuild

So:
# yum install rpm-build

For other possible candidates for development packages, have a look at 
the results of:
# yum grouplist | grep Devel

Phil