Sigh, yes you are right, I meant that it is case sensitive. Thanks for
th correction. I tried to point it out only because the OP mentioned
"xx" in one sentence, then showed "XX" in his example. I like your way
using UPPER, as long as it is ok to change the result to upper case.

Len

T. Valko wrote:
it isn't case sensitive, so to replace both upper and lower case, use 4
levels of nesting.

I think you meant it is case sensitive (which it is) but you don't need to
nest 4 levels.

Try it like this:

=SUBSTITUTE(SUBSTITUTE(UPPER(A2),"XX",""),"YY","")

Also note that if the string is XXXZZZ

The result will be XZZZ