Thanks, Naomi

Your method works fine, but, if I understand correctly, it won't work with SQL Server 2000, so Sergey'd method would be helpful there.
Is that correct?
>>SELECT t1.sono, t1.tcode, t1.tdate ;
FROM mytable t1 ;
WHERE t1.tdate = (SELECT MAX(tdate) FROM mytable t2 ;
WHERE t1.sosno = t2.sono)