how many inserts in one transaction?

Hi,

I have a database created in postgres 6.5.3 and need insert huge
number (~10-100 thousands) of
rows in one of tables. To do that quickly I put this part of work in
transaction. My question is such: should I split this block of
insertings into many transaction to raise the speed? And
exists the limit of INSERT-commands that I can do in one transaction?

Best regards,
Alex