I've traveled out of state with it but never out of country. You buy the plan you want and insert the T-Mobile SIM card. I had a really good plan at $10 for 5 G

I've traveled out of state with it but never out of country. You buy the plan you want and insert the T-Mobile SIM card. I had a really good plan at $10 for 5 GB a month which was plenty, because even if I ran out afterwards, which I hardly ever did (T-Mobile doesn't count data for Netflix or Pandora anymore), but it would just slow down to 3G speeds, which was still fast enough to check email and read webpages. I think I upgraded to another plan for $25 a month for unlimited data, not that I personally upgraded, but someone in my family needed to upgrade which automatically upgraded my plan. The SIM Card is a phone line with its own phone number. Of course, you can't call it or receive calls, but its technically acting like a cellphone with Internet. So as a phone line, you are connecting to a cell tower. So I can assume that if you go out of country, like any phone, you can enable roaming and it will find towers close by and use those, but those data rates could probably get expensive. Although T-Mobile is trying to become a true power player in the game against AT&T and Verizon and has definitely started to offer some really great plans. Read this: http://www.pcmag.com/article2/0,2817,2425436,00.asp http://www.pcmag.com/article2/0,2817,2425436,00.asp -- looks like you can get on a plan that will cover you completely so you pay nothing. I know when my brother visited Canada and turned on his phone, he received a text message from T-Mobile that he could "continue making calls and texting without any worries about data rates." If you aren't covered in a specific country, I'm pretty sure you can call up T-Mobile and see if they can offer you a temporary package deal for like a month or a "pay as you go" deal if needed.