You can use the DCount Domain Aggregate function:
DCount("*", "[NameOfTable]", "[NameOfYesNoField] = True")
You can also use SQL:
SELECT Count(*) AS TotalYes
FROM NameOfTable
WHERE NameOfYesNoField = True

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Doug Steele, Microsoft Access MVP
http://I.Am/DougSteele
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>I have a with field with yes/no values and need to count the number of "Y"
> (yes)responses on a report. What syntax/code can I use to count only the
> Y
> values?