Do you mean ...
SELECT COUNT(*) as counter
FROM table1
LEFT JOIN table2 ON ( table1.item1 = table2.item2 )
WHERE item3 = 'X'
... or even just ...
SELECT *
FROM table1
LEFT JOIN table2 ON ( table1.item1 = table2.item2 )
WHERE item3 = 'X'
... and use mysql_num_rows() to count the returns.
Paul 🙂