As one of the (perhaps) foolish few institutions that circulates all of our
periodicals (both bound and unbound), and as one who has recently undergone
reclassification of the entire periodical collection (from shelving by title
to shelving by call number), I can share some of the lessons that I'll never
forget---

As for call numbers:  Most of the time I use the same call number when a title
changes.  We have found that this makes it easier for the student assistants
to shelve and for the patrons to find.  It is especially useful for those
piddly changes (like Atlantic to Atlantic Monthly to Atlantic and back again)
that are all bound in the same color and would be a horrible mess if the
cutter were changed for each title change.  It can make it a bit more difficult
for the Technical Services staff to get the right record by call number, but
if you stress the importance of looking for closed dates in the 362, then it
(usually) goes OK.

You see that I say above "most of the time."  There are several cases where
it is necessary to have different call numbers--obviously in cases of mergers
and splits, they can't all carry the same number.  And on those happy occasions
that the volume numbering begins again with a title change, you really need
a different cutter (even if it's really the same journal) or the students and
patrons get helplessly confused, because you have two vol. 1's, then two
vol. 2's, but with different dates and they don't know what to do with them.

As for basing numbers on subject matter or publishing history, that's more of
a judgement call.  The case of _Broadcasting Yearbook_ comes to mind, when it
changed to _Broadcasting Cablecasting Yearbook_ (and I believe has made
several more irritating changes in the past three or four years--like
_Broadcasting Cablecasting Marketplace_ -- or am I confusing that with yet
another?)  Anyway, the addition of the "Cablecasting" business changed the
class number entirely and by changing the call number the volumes were split
up.  I believe that _in general_ patrons are looking for something on a given
subject and have looked up citations in an index and then go to the stacks
to get their information.  Since the whole idea of shelving periodicals/serials
by class number rather than title is to group like subjects together, it is
usually a better idea to follow the subject of a title rather than the title
history.  However, this isn't a hard and fast rule, and if some well-known
title that might be used more for browsing changes focus (and title) a bit,
it might be better to leave them all in a run.

Oh, aren't serials grand!?

Good luck.

Rebecca House Stankowski
Technical Services Librarian
Purdue University Calumet
Hammond, Indiana  46323-2094
stankorh@pucal.bitnet