I thought that too, but space has been opened up:

http://travel.state.gov/content/travel/english/legal-conside...

but only if the act is performed (1) voluntarily and (2) with the intention of relinquishing U.S. citizenship.

Is the key point.

Here's a pretty good dual citizenship FAQ compiled over the years by Rich Wales:

http://www.richw.org/dualcit/ - start here

http://www.richw.org/dualcit/faq.html - the meat of it is here

Yes it does, but people do it anyways.

If you become a U.S. citizen, you're expected to renounce your other nationalities.

Edit: The biggest case was Facebook co-founder Eduardo Saverin renouncing U.S. citizenship for the tax savings

http://en.wikipedia.org/wiki/Eduardo_Saverin

2nd Edit: some discussion on Hacker News

https://news.ycombinator.com/item?id=3979669 https://news.ycombinator.com/item?id=4416258

You can become a U.S. citizen and maintain citizenship of your country of birth(or others your are holding)if the country wasn't China and a few others listed in the link I have provided. Half of my immediate family have become U.S. Citizens and maintained their other citizenships.

http://www.immihelp.com/citizenship/dual-citizenship-recogni...

I was told by a friend who's getting U.S. citizenship you have to take an oath renouncing other citizenship.. here it is:

"“I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty of whom or which I have heretofore been a subject or citizen…” from the Oath of Allegiance "

http://www.newcitizen.us/dual.html

apparently it is not binding:

" the oath has never been enforced to require the actual termination of original citizenship"

http://en.wikipedia.org/wiki/United_States_nationality_law#c...

Edit: can you ask your family if they took that oath, or is the information obsolete? Until now, I thought it was an actual requirement to renounce other citizenships.

That is still the oath they make you take, but it has no legal consequences. You take it, eat the brownies that the VFW baked for your naturalization ceremony, and happily keep both passports.

Source: happily kept both passports.

The US doesn't seem to care - they still treat their citizens as citizens, and sort of ignore any other citizenship. Unless there's a real conflict, like joining a foreign military.