"Ingrid Voigt" wrote...
I've got matrices in my worksheet I'd like to
multiply using MMULT. However, as long as some
of the cells referred to are empty, I can't
get a result. Excel apparently doesn't set the
contents of these cells to 0 as I'd like it to.
....

Since you'd be entering these as array formulas anyway, if RngA and RngB
have blank cells, try

=MMULT(RngA+0,RngB+0)