Originally Posted by Indecisive

"As a U.S. citizen or resident alien, your worldwide income generally is subject to U.S. income tax, regardless of where you are living. Also, you are subject to the same income tax filing requirements that apply to U.S. citizens or resident aliens living in the United States."

irs dot gov, Publication 54 (2007), Tax Guide for U.S. Citizens and Resident Aliens Abroad