Use SELECT DISTINCT or SELECT DISTINCTROW.  If you are using the query GUI,
in the properties of the query, say Yes to either Unique Values or Unique
Records.

Write the query correctly.

If you would like help doing so, please give us some help! We cannot
see your computer, and have no way of knowing what the query is, or
what it's doing.

Please open the Query in design view; click the dropdown tool on the
leftmost toolbar icon and select SQL. Copy and paste the SQL text
(which is the real query, the grid is just a tool to create SQL) to a
message here. It might help to indicate how your tables are related
and what you're seeing duplicated.

                 John W. Vinson[MVP]