http://en.wikipedia.org/wiki/United_...ion#Amendments
Article Five
Article Five describes the process of amending the Constitution. It provides for two methods of amendment ? either two-thirds of the state legislatures can request a convention for the purpose of considering amendments, or a two-thirds majority of both houses of Congress can pass them. After this step, all proposed amendments are sent to the states, three-fourths of whose legislatures or conventions must ratify them before the proposal can become a part of the Constitution. Article Five also sets limits on the ability to amend the Constitution, although these limits are extremely broad.