I have read the regulation that a landed Canadian immigrant will have to have a valid visa stamp to re-enter US even within 30 days of stay in Canada, which means the automatic visa revalidation doesn't apply. The rule was in effect starting from March 2003. But from what has been posted here, many people have successfully return to US without a visa stamp after landing Canada. Anybody cares to explain what's going on? I expect to land Canada sometime soon. Many thanks.