Oracle: Output not shown even if SERVEROUTPUT variable set to ON
As you can see from the output below, a test anonymous PL/SQL block works in SQL Plus as expected:

[oracle@node1 ~]$ sqlplus phil/phil

SQL*Plus: Release 11.2.0.2.0 Production on Mon Oct 1 21:55:35 2012

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL&gt; set serveroutput on
SQL&gt; DECLARE
  2      v_rec_count number;
  3  BEGIN
  4      select count(*) into v_rec_count from dual;
  5      dbms_output.put_line ('count: ' || v_rec_count);
  6  END;
  7  /
count: 1

PL/SQL procedure successfully completed.

SQL&gt;


I'd guess that you're not using SQL Plus to test &amp; are testing in another tool (such as SQL Developer) and it's not set DBMS_OUTPUT.enable() or you haven't configured the tool to correctly display the output from the RDBMS.

Or, it could be the fact that SET SERVEROUPUT ON is a typo :)