I would say - at least - 25%. You should be diversified - some large stock funds, some overseas funds, some index fund, and a bond fund. I think the European markets and Asia offer great value. The EU is 400 million people. India and China have over a billion inhabitants each. They both have rapidly growing middle classes. The USA is a debtor nation - our trade deficit is enormous - all the dollars are going overseas. The Federal deficit is huge. What has helped is having China and the Middle East countries investing those trade dollars in US Treasuries. How long will this last? Europe, Japan, China and India are gowing faster than the US at the moment. In short, don't have all your 401K assets in dollars - an international fund gives you some protection against a devalued US dollar.