hi Andrew, long time no talk, this is Frances, posting under a different
 name (for various reasons..  all innocuous ...;)

first of all, I did change my if-clause to your above line,
 if (theSponsor == null || theSponsor.trim().equals("") ) {
thank you..  (I had forgotten that null-test should always go first..)

it turns out that, just as I thought, this problem has to do w/tiles and
variable scope; don't know if you know struts/tiles, I just learned,
after talking to a knowledgeable java guy here, that each tile gets
converted into a different servlet, which raises a whole lot of
variable-scope issues (since then presumably there is a different
jsp_service() method for EACH TILE...)

what I ended up doing:

in controller page (page that calls the tiles, don't know if this
correct terminology, this is what we call them here):

<%
  String theSponsor = "";
  theSponsor = request.getParameter("sponsor");   
   if (theSponsor == null || theSponsor.trim().equals("") ) {
    response.sendRedirect("/ws/sponsors/index.jsp");
}
%>

tiles-code here...

in tile itself then, had to declare a new var to grab same param but
with a different name, thus:

<%
  String theSponsorA = "";
  theSponsorA = request.getParameter("sponsor");
  if (theSponsorA != null || !theSponsorA.trim().equals("") ) {
    %>

    CUSTOM-TAG HERE, with var above as a param-value..

<% } %>

hope this makes sense, at any rate this is what worked...

thank you for your help..