I'm probably dense but I'll post my problem and the (of course) very
simple solution and will hopefully save someone else a day of
hair-pulling.

Problem: Couldn't get a simple Master-detail link to work using
TADOTable.
I set the MasterSource and MasterFields properties if the detail table
to the appropriate datasource, fields of the intended master--just
like
I was accustomed to doing with good 'ol TTable TDataSet.

When things didn't work I saw this DetailFields property and, well
since
I was setting the MasterFields on the Detail table I assumed I'd set
the
DetailFields property on the Master Table!-----WRONG!!!!

SOLUTION:
In TTable, setting the MasterFields property of the detail table
automatically
lists both Master and Detail fields. You choose one from each column
and
voila, they're linked. Linking turns out to be a 2-property process
with the
ADO Data components. You have to set both the MasterFields AND
DetailFields
properties of the ***DETAIL*** table.  

Painfully obvious now...