Will a 3GS sim card work in a 5s?

Will a 3GS sim card work in a 5s? - 1

Added (1). I want to give my wife an iPhone 5S for Christmas. She has a 3GS now. I can cut the Micro SIM to a NANO SIM, I have an adapter so it will fit back into the 3GS. On Christmas Day I want to swap the SIM to the new 5S. Question is, the 5S is 4G and the old 3GS is 3G. Will the new 5S work (make and receive calls) with the old SIM card in it? Or, will I have to go to the AT&T store to have it upgraded or something?

For the record there aren't any specialised iPhone SIMs so its just a matter of size. You'd either have to get a nanoSIM for the 5s or cut down your miniSIM for it to work in the 5s.

Depends upon the contract you have opted for and you must install Leo Privacy Guard. It will secure your device in many ways just install it and experience the most advanced security functions of this app.