Take your phone and phone number
The first thing to determine is whether your current cell phone will work overseas.

Do you have a multi-band GSM phone? GSM stands for Global System for Mobile Communications, the standard technology used by cell phone providers in more than 200 countries.

If you have a dual- or tri-band GSM phone you can make calls using a GSM network in other parts of the world. You'll be able to take your phone and your phone number with you on your overseas trip.

U.S. carriers selling GSM world phones include T-Mobile, AT&T, Cingular and Nextel. If you're using a multi-band GSM phone in the U.S. you'll need to activate the phone so it works on international frequency bands. Be sure to contact your carrier before your trip.

"The upside is it's the simplest way to go and you get to keep your phone number," says Scott McNeely, digital publisher at Lonely Planet Publications. "The downside is it can be kind of expensive, particularly if you're going to be on the phone for more than a couple of minutes at a time."

As handy as it may be to take your cell phone overseas, you'll get slapped with some serious international roaming charges. You'll pay $1 to $2 per minute for any call you make or receive in Europe. And calling rates are even higher in other parts of the world. Some carriers charge activation and other fees for worldwide service. Be sure to check.

Take your number, buy or rent a phone
Another way to keep your cell phone number when you travel is to remove the Subscriber Identity Module (SIM) card from your phone and place it in a handset that operates on international frequencies. The SIM card, which is about the size of a thumbnail, stores your personal information, including your phone number and address book. Call your carrier to make sure your SIM card is able to work overseas.

The downside to bringing your SIM card overseas is the cost. You'll be zapped with hefty international roaming charges and other fees. For example, AT&T charges $25 for a SIM card programmed with a customer's personal information and $7.99 monthly fee for its WorldConnect service.

You'll also need to buy or rent a GSM phone that works overseas.

Rent a phone
Rental fees on overseas phones vary widely. You'll pay about $7 or $8 per day and $30 to $50 per week. Monthly rates are anywhere from $50 to $150 per month.

You'll want to shop carefully. Per-minute calling rates vary widely. Some cell phone rental companies charge shipping fees of $15 to $35. Others charge $2.50 fee for itemized billing.

Companies that rent wireless phones to global travelers include InTouch USA, Planetfone, Rent-a-Cellular, WorldCell, Roadpost, Cellhire, Cellular Abroad and Telestial.

Some rental car companies will toss in a "free" cell phone rental with your European car rental. They include Avis, Alamo, Renault Eurodrive and Europe by Car.

You may not have to pay a daily or weekly rental rate for the phone but you'll still have to pay for any calls you make and receive. Be sure to ask about per-minute rates. That "free" phone could be saddled with a lousy per-minute rate.

You'll also want to watch out for fees. Europe by Car charges a $40 delivery-and-collection fee on its "free" cell phone rentals. Avis charges a $25 delivery-and-collection fee plus a rental fee of $5 a day if you keep a cell phone more than seven days.

"One way or another, the phone isn't free," says Ed Perkins, a nationally syndicated travel columnist and consumer advocate.

Buy a phone
If you're going for a long vacation or you make frequent trips abroad, you may be better off buying a phone that works in your destination country.

For example, Nextel customers have the option of renting a phone through Cellhire for $8 per day or $99 per month or buying a P280 phone, which is designed to work on the specific GSM network used in 90 countries. The P280 phone has a price of just $49.99. It requires a one-year or two-year contract and comes with a $35 set-up fee.