Do I need to register my cell phone in Turkey?

Have you asked T-mobile? Seems to me that is where I would start.

Doubt it-I have a Verizon phone and other than telling Verizon I'd be there and the EU, it worked perfectly.

I took my TMobile phone all around Turkey with me last October and it worked just fine. I did not register it or notify anyone. It worked everywhere and when I got home I had only been charged 20 cents per minute for calls. Data was free. The only thing that was hard to do was make wi-fi calls...I tried this numerous times as wi-fi calls are free instead of 20 cents. For some reason, although I could turn on wi-fi to do internet and emails, the calling seldom worked out.

I just wanted to add something I came across this evening while reading on this website: turkeytravelplanner.com. Here's the public Facebook as well - updated very often. https://www.facebook.com/TurkeyTravelPlanner. The website is quite helpful - it's written by an American who loves Turkey and travels there a lot. He had an update this week that says the Turkish government used to require visitors to register their cell phones after 60 days and that they've just now made it 120 days before you need to register. He's a link to the information, but it's in Turkish:( http://www.haberturk.com/ekonomi/teknoloji/haber/1137991-turistlerin-cep-telefonu-kayit-suresi-uzatildi

Valerie, thanks for pointing me to the Facebook post of Turkey Travel Planner. I now understand that I will only need to register my cell phone if I plan to stay for an extended period of time. I will only be there for a week, so it is N/A for me.

Frank, thanks for your reply. I checked with T-Mobile and while they don't know anything about the requirements in-country, they said that Turkey is on the list of countries that are automatically covered under my plan, so there are no roaming charges.

JerryG, thanks for your reply. Based on your response and Valerie's, I am assured now that my cell phone will work in Turkey.

Kat - if you're just coming for that short trip you mentioned in another post, then yes your cell phone will work. Turkey would block unregistered phones after a longer period of time. That's for people living here, not short vacation trips. It's usually 2-3 months before they get blocked. Assuming you have a GSM phone, it will work.

I mentioned this before in forum. Yes its going to work up to 2 months. After 2 months, its going to be blocked. Best way is to buy prepaid simcard at arrivals at Istanbul Airport at Vodofone Kiosk. You wont miss it at Arrivals. You just need a passport . Thats it. Having internet is on your phone is very helpful especially to use maps.
2GB internet ,1000 SMS , 500 minutes calling time is 23 tl ( $8USD)at Vodofone or you can check other plans at :
http://www.vodafone.com.tr/Tarifeler/Altin-Tarifeler.php