Comparing Dates

Why does the following occur?

SQL> r
  1 select * from brit_attr_value where TO_DATE(attr_value) between   2* sysdate and sysdate+7;
ERROR:
ORA-01858: a non-numeric character was found where a numeric was expected

        attr_value is a non-null varchar2(25) in the form DD-MON-YY, so it should be easily converted by the TO_DATE function. This works fine in ProC, but fails when run directly from SQL.

          Any ideas?

        Brit Willoughby
        Brit.Willoughby_at_WichitaKS.ATTGIS.Com