Paris is a very safe city, though you might come back from a metro ride and realize that your wallet was stolen :-(

No violence, but it is very unpleasant!!!

It happened to me, to people I work with, and to some of my guests...

Often pick-pockets are young, like teenagers, and not French...

So, pls, hide your wallet properly, do NOT use an iphone or anything similar in the metro.

Some general pieces of advice:

1.  Passports:  Leave your passport in the apartment.
2.  Money:  Don't carry a lot of cash.  Use the ATMs and your credit cards.
3.  Passport Photos:  Bring an extra set of passport photos on your trip.  It is difficult to find a place to have photos for US passports in Paris and is costly.
4.  Copies of Important Documents:  Bring copies of important documents, your credit cards, etc on your trip and leave another copy with friends at home.

In any case, you can have your passport replaced at the US embassy, which is located right off the metro stop Concorde,
2 Avenue Gabriel
75008 Paris, France
01 43 12 22 22
http://www.embassy-worldwide.com/embassy/u-s-embassy-in-paris-france/