SQL group by select

I am using SQL Server and I have a table with the following columns:

SessionId | Date | first name | last name 

I would like to do group by sessionId and then get the row with the max date.

For example:

xxx | 21/12/2012 | f1 | l1
xxx | 20/12/2012 | f2 | l2
yyy | 21/12/2012 | f3 | l3
yyy | 20/12/2012 | f4 | l4

I would like to get the following rows:

xxx | 21/12/2012 | f1 | l1
yyy | 21/12/2012 | f3 | l3

Thank you