SQL Query to fetch information based on one or more condition. Getting combinations instead of exact number

I have two tables. Table 1 has about 750,000 rows and table 2 has 4 million rows. Table two has an extra ID field in which I am interested, so I want to write a query that will check if the 750,000 table 1 records exist in table 2. For all those rows in table 1 that exist in table 2, I want the respective ID based on same SSN. I tried the following query:

SELECT distinct b.UID, a.* 
  FROM [Analysis].[dbo].[Table1] A, [Proteus_8_2].dbo.Table2 B
  where a.ssn = b.ssn

Instead of getting 750,000 rows in the output, I am getting 5.4 million records. Where am i going wrong? Please help?

via Chebli Mohamed