Hi Jonathan

>Might this be what you're after?

Almost, see changes below

lcSQLTable = "MACCOUNTS"
*--Passed the name of a Firebird table, returns its primary key
*--Assumes giHandle contains previously-established connection handle
LOCAL lcSQL
TEXT TO lcSQL NOSHOW PRETEXT 15
     SELECT RDB$FIELD_NAME AS COLUMN_NAME
          FROM RDB$INDEX_SEGMENTS I
               INNER JOIN RDB$RELATION_CONSTRAINTS C
                    ON C.RDB$INDEX_NAME=I.RDB$INDEX_NAME
          WHERE RDB$CONSTRAINT_TYPE='UNIQUE' AND
               RDB$RELATION_NAME=?m.lcSQLTable
ENDTEXT
SQLEXEC(giHandle,lcSQL)

This will return the cursor containing all fields involved in the UNIQUE constraints. Thanks, without your help I would not know how to go about it.