I am using Access 97. I have a subform in which I have the following two fields:

account number (100)
account number description (Office Supplies)

I want the description field to autofill when the user enters the account number.

I also have another table not the same one linked to the subform that has just two fields, account numbers and related descriptions.

I tried the help in Access for autofill. But it is not working.

Assuming tblAccounts is the table you have with two fields, AccountNumber and AccountDescription then you could do this:

Private sub txtAccountNumber_AfterUpdate(0
Forms![subfrmSomeName]![txtAccountDescription] = DLookup("[AccountDescription]", "tblAccounts", "[AccountNumber] ='" & Forms![subfrmSomeName]![txtAccountNumber] & "'")
End Sub

I referenced your sub form as subfrmSomeName in this code.

ntp

This code is very clear and works! Modifications may be required, such as removing the "txt" before the Field Name, and if your form field is based on a query rather than a table. Thanks to ntp! cft