Try this:

=SUMPRODUCT((A1:A100="Production")*(B1:B100="Exter nal")*C1:C100)

You can't use total column references (A:A).

Also, you could refer to cells containing your criteria, instead of
'hard-coding' them in the formula itself.
That makes criteria changes easier to accomplish.

=SUMPRODUCT((A1:A100=D1)*(B1:B100=D2)*C1:C100)

--
HTH,

RD

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"luvthavodka" wrote in message
...
I have the following table, and would like to sum the value of C with the
criteria A=Production, and B=External. I have so far
SUMIF(A:A,"Production",C:C)...but can't work out how to add AND B:B,"
External". In this case the return for my request will be C1 + C5

A B C
Production External £28,240
Design External £71,908
Production InterGroup £159,070
Design External £3,600
Production External £327,700

Thanks for any help offered!