We just went to Belize in April 2004 and at that time cruise ship passengers did not need passports. Having said that, we have them anyway for ourselves and our children. If something happened during the cruise and we got left behing at any port, or had to make an emergency evacuation, we very well could need the passports in order to leave a country. I read on another board where someone had missed there flight and the ship left and they had to join up in progress. They almost didn't get into Belize, their first port, to join the ship as they did not have a passport. I would urge anyone traveling outside the US to get one. As a previous posted pointed out you never know when the laws will change. Just my 2 cents.