I have both a UK passport and a US passport (born UK, naturalized US), and almost all my international travel is between those countries.

Since I carry both passports, can I freely choose which one to use when entering either country (eg: whichever line is shorter), or is it better to pick one passport and stick with it?

So far I've been travelling exclusively under my US passport for fear that a US customs guard would be disturbed that my US exits and entries don't add up. But is that a real fear? Does it matter to them if, for instance, my US passport is mainly entry stamps because I've used my UK passport to enter the UK?

Thanks.

 

Thanks --

My concern is that, for instance, my US passport would only show entry stamps for the US, not for the countries I visited, and that the unfriendly souls at the US Immigration Desk will want to know where I'm coming back from, since I don't appear to have been anywhere.

If they're quite accustomed to people using their US passport only to enter the US, then I have no problem, but given that I forswore all other allegiances (in their eyes at least) when I took US nationality, my fear is that they'll take issue with me behaving otherwise.

The British, I imagine, couldn't care less.