Select * 
from mytable
Where mytable.date 
Between TO_DATE(@startdate,'MM-DD-YYYY') 
And  TO_DATE(@@enddate,'MM-DD-YYYY')

DECLARE
param_bdate DATE;
param_edate DATE;
SET param_bdate = TO_DATE('01/15/2010','MM/DD/YYYY');
SET param_edate = TO_DATE('01/15/2010','MM/DD/YYYY');
Select * from mytable
Where mytable.date Between param_bdate AND param_edate ;

VARIABLE STARTDATE VARCHAR2(11)
EXEC :STARTDATE := '01-JAN-2012'
VARIABLE ENDDATE VARCHAR2(11)
EXEC :ENDDATE := '10-JAN-2012'
SELECT *
FROM MYTABLE
WHERE MYTABLE.DATE BETWEEN TO_DATE(:STARTDATE, 'dd-mon-yyyy')
                       AND TO_DATE(:ENDDATE, 'dd-mon-yyyy')
;

SQL> 
SQL> variable startdate varchar2(11)
SQL> exec :startdate := '01-JAN-2011'
PL/SQL procedure successfully completed.
 
SQL> variable enddate varchar2(11)
SQL> exec :enddate := '31-DEC-2011'
PL/SQL procedure successfully completed.
 
SQL> select created from v$database where created between to_date(:startdate, 'dd-mon-yyyy') and to_date(:enddate, 'dd-mon-yyyy') ;
CREATED
------------------
11-AUG-11
 
SQL>