=SUMPRODUCT(--(A1:A100="X"),--(B1:B100=""),C1:C100)
you can not use whole columns (eg. A:A, B:B, or C:C) unless you are using
XL-2007

"Caroline" wrote:

I want to sum amounts from one column if 2 other columns meet the criteria I
defined.
Here is what I have: =IF(AND(A:A="x",B:B=""),SUM(C:C))
Even though I have a lot of rows that match both criteria (have an "x" in
column A and nothing in column B), the formula returns "false".
Any ideas? Thanks!