How to delete old yumdb entries?

Hi,

I always upgrade my Fedora OS and this seems to have lead to a lot of
old entries in my yumdb for old packages from previous versions of
Fedora, which take quite a bit of space.  Is there anything special I
need to do to delete them or do I just use rm?

Commands below suggest at about 3/4 of the entries are for old
packages from previous versions of Fedora.

Thanks,
Mike

-- 

[root@rockover ~]# du -sk /var/lib/yum/*
5896    /var/lib/yum/history
4       /var/lib/yum/rpmdb-indexes
4       /var/lib/yum/uuid
129596  /var/lib/yum/yumdb

[root@rockover ~]# ls -d /var/lib/yum/yumdb/?/* | head -4
/var/lib/yum/yumdb/a/002f1226390a46fd0ff71aa7a7f14a910a046081-audit-libs-devel-2.0.4-3.fc13-i686
/var/lib/yum/yumdb/a/01d4527ce1e596b21c07f91f564eccc4dd1dcbed-avahi-autoipd-0.6.25-7.fc13-i686
/var/lib/yum/yumdb/a/03124cecb88e0ca3ce72b99b08439031bd8e3121-audacious-1.5.1-9.fc10-i386
/var/lib/yum/yumdb/a/0462005cb5df44a3ebf8507caacd0fa4bd7bc4ce-abrt-plugin-runapp-1.1.14-1.fc13-i686

[root@rockover ~]# rpm -q audit-libs-devel avahi-autoipd audacious
abrt-plugin-runapp
audit-libs-devel-2.1.3-1.fc14.i686
avahi-autoipd-0.6.27-8.fc14.i686
audacious-2.4.5-1.fc14.i686
abrt-plugin-runapp-1.1.18-1.fc14.i686

[root@rockover ~]# find /var/lib/yum/yumdb -name '*.fc*' -print | sed
's/.*\(\.fc[0-9][0-9]*\).*/\1/' | grep '^.fc' | awk '{c[$0] += 1}
END{for(l in c) printf "%6d %s\n", c[l], l}' | sort -n
     1 .fc3
   143 .fc10
   664 .fc11
  1458 .fc13
  1565 .fc14
  1642 .fc12