what's wrong with this IF statement

Is there a problem with the following syntax?  Even though IOUT is .false. and IHEAD=1 and ITAIL=400, the code still runs the statement inside the IF.  I can even select the entire expression inside the IF (   )  and the debugger says it evaluates to FALSE.  What the heck is going on?

        IF (IOUT .OR. IHEAD .GT. ITAIL) THEN
           CALL UMD2ER (1, ICNTL, INFO, -3, INFO (19))
        ENDIF