First, sort to get the data in order.  This BY statement might be overkill, because I'm not sure if DATE is character or actually represents a SAS date.  It will work either way, however, AS LONG AS YOUR MONTH values are consistent.  You can't store month with leading zeros just some of the time.  You need to have them or omit them consistently, to get the right order: proc sort data=have; by no year month date; run; Then to get the most recent values: data want;    update have (obs=0) have;    by no year;    drop date month; run; I have to give credit somewhere, but I'm not sure to whom.  A similar solution had been proposed to a similar question at some point. Good luck. ... View more

SQL can do it easily. data one;   input serial start $15. ; cards; 101 jan2008 101 feb2008 101 march2008 102 feb2007 102 march2007 102 april2007 ; run; data two ;   input serial end $15.; cards; 101 july2007 101 aug2007 101 sept2007 102 may2008 102 june2008 102 july2008 ; run; proc sql ; create table want as   select * from one    where serial in (select distinct serial from two) outer union  corresponding   select * from two    where serial in (select distinct serial from one); quit; proc sort data=want;by serial;run; Ksharp ... View more