I agree with the above about computers (I used mine in Germany with only an adaptor), but you may want to get a transformer, too, if you travel with other electronics. That's the "box" that actually changes the current to the right level for appliances you use in the US. At then end of my trip to Germany, I plugged my cell-phone charger into the outlet with only the adaptor. Oops. I heard a little static "pop" and that was the end of the charger. It was more out of habit since I'd gotten used to it with the computer. If you need to recharge a cell phone or a digital camera battery, it will come in handy.