Wow! Thanks guys...
I never would never have been able to solve this "mysterious problem"
without your help.

Thanks again,
Bernie

"bw" <iamnu@cableone.net> wrote in message
news:11m1htg99sd8q59@corp.supernews.com...
> =AVERAGE(IF(MONTH(B$5:B$200)=J2,H$5:H$200))
>
> The above array formula is used in 12 different cells, for each month of
> the year. All of the formulas generate the proper values, except for
> Month 1 (January).
>
> For January, and January ONLY, this formula only works when the range is
> the exact same size as the last date in the worksheet.
>
> For example:
> Row 65 contains the last date (in Column B), Rows greater than 65 contain
> null values for the date (Column B), and null values to average (Column
> H). So when J2 has a value of 1, the formula only works when I change it
> to the last row as follows:
>
> =AVERAGE(IF(MONTH(B$5:B$65)=J2,H$5:H$65))
>
> Can someone give me a hint as to what may be the problem here?
>
> Thanks,
> Bernie
> p.s.
> Data is sorted by date (column B), and the formula works for all months
> except January.
>