Transaction Isolation - read uncommitted

Hi all,

i am trying to find a way reading uncommitted data within a single
transaction, but it seems there is no way
to do a "TRANSACTION_READ_UNCOMMITTED" on connections in Postgresql as
it works for Oracle or Informix.
I there any support in postgres for reading uncommited data without a
read lock ? I am currently using JDBC/PostgreSQL 7.1.2 running on Linux.

Thanks;
Ralf