union with count?

Hi dudes, i have the following question
i have 2 tables with the same format, and i want to know if is there a 
possibility of using some sort of count(*) for achieving this result:
select a from table1 where (condition) union select a from table2 where 
(condition), count(a) group by a

The idea is having how many times (condition) is true for both tables.

Im not shure im explaining myself clearly, my english is not the best 
(as you can see ;)


Thanks!
Gerardo