It depends on where you're going, really. If it's a country where ATMs abound and credit cards are widely accepted, then I would go with a little cash and my bank account or credit card well topped up. Otherwise, US dollars seem to be the preferred currency in pretty much every country in the world. When withdrawing money from a foreign ATM, you will pay a fee - usually a small percentage (3-5%) of the amount withdrawn. I usually withdraw a couple of hundred at a time, keeping the number of withdrawals fairly low. Loading your credit card account with funds before you go is a good idea. Bear in mind that most credit card companies start charging a high rate of interest as soon as you withdraw cash, so it's worth having the funds in place beforehand, rather than running up a bill that will have to be cleared later.