IS there a limitation in Jewish law regarding the size or dimensions
of the kosher scroll that goes into the mezuzah case? I've seen
scrolls advertised which measure from about 2.5 inches to 8 inches
within the dimensions of a square. Could the scroll be as large as 16
inches, or as small as a square postage stamp? Please cite sources for
answer.

Dear ssy,

My research on this topic revealed that production of a proper mezuza
(or, more commonly,  mezuzah) scroll is indeed subject to a number of
guidelines. The following things are determined explicitly:

- Who is qualified to write a kosher scroll
- The scroll needs to be handwritten to fulfill its purpose
- What kind of ink shall be used
- What special kind of writing must be used
- The appearance of the text
- The text itself
- What kind of parchment is adequate
- What erasures are allowed

But, surprisingly, the size of the parchment is not mentioned
anywhere. While nearly all other aspects of the producton of mezuzah
scrolls are accurately regulated, rabbis all over the globe seem
silently to agree that a scroll's size does not affect whether it
pleases Him.

Of course, it is not very satisfactory to derive conclusions from the
fact that something is apparantly not constituted anywhere. In this
case, however, it is a clear statement: The mezuzah scroll's size does
not matter, otherwise this would show up among the other instructions.
Rabbi Scheinerman (see sources below) says on her website only that "A
mezuzah scroll is usually approximately two to three inches square."
The use of the word 'usually' indicates articulately that these are
only common dimensions, but not measurements based upon religious
regulations.

Choice of sources used:

Rabbi Scheinerman's Home Page - What's What?, by rabbi Amy R.
Scheinerman,
http://scheinerman.net/judaism/synagogue/objects2.html#mezuzah

Internet FAQ Consortium - Question 11.9.4: Symbols: What is a Mezuzah?
http://www.faqs.org/faqs/judaism/FAQ/05-Worship/section-71.html

Judaism 101 - Signs and Symbols, by Tracey R. Rich, 2001
http://www.jewfaq.org/signs.htm#Mezuzah

The World Of The Mezuzah, by the Chicago Community Kollel, 1999
http://cckollel.org/html/heritage/questions/question93.html

MezuzahDoctor - What is a Mezuzah?
http://www.mezuzahdoctor.com/MEZUZAH/MEZUZAH1.htm

Search terms used:
"mezuzah scroll" size:
://www.google.com/search?q=%22mezuzah+scroll%22+size&hl=de&lr=&ie=UTF-8&oe=UTF-8&newwindow=1&start=30&sa=N
mezuzah "proper scroll":
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=mezuzah+%22proper+scroll%22&meta=
mezuzah "kosher scroll":
://www.google.de/search?q=mezuzah+%22kosher+scroll%22&hl=de&lr=&ie=UTF-8&oe=UTF-8&newwindow=1&start=30&sa=N
mezuzah scroll square:
://www.google.de/search?q=mezuzah+scroll+square&hl=de&lr=&ie=UTF-8&oe=UTF-8&newwindow=1&start=20&sa=N

Hope this answers your question!
Regards,
Scriptor

Being a patient persistent, stubborn, (oh all right, obsessive)
individual, I can usually dig out info I need either on line (ideally
suited to my nature), or using library and human resources. Your
answer corroborates the information I found, so after an investigation
of several months' duration, I can let go of the subject. Many thanks.
PS. If you happen to run across more stuff, please forward it to me.