with regard to international travel, an individual may transport any amount of cash without interference from homeland security/border patrol if the amount does not exceed US$10,000. if the amount is US10$,000 or more, then the traveler is required to complete a specific u.s. customs form and submit prior to exiting or entering the u.s. i have personally experienced being stopped by u.s. customs inspectors on the jetway leading to the aircraft. they asked my wife and i to step aside (not that there were many people behind us because it was the first class jetway) and began asking us a series of questions. when it came to the amount of cash we each were transporting, we responded that we were carrrying $9,900 each, just below the threshold of having to file the u.s. customs form. on another occassion, i carried more than US$30,000 but had filled out and submitted the appropriate u.s. customs form declaring the full amount. on that occassion, no inspector approached or even looked at me during the boarding process. i would caution anyone who attempts to circumvent the law will more than likely be caught. there are u.s. customs/homeland security inspectors that are stationed in strategic foreign gateways just for this sort of thing.