Before an amendment can take effect, it must be proposed to the states by a two-thirds vote of both houses of Congress or by a convention called by two-thirds of the states, and ratified by three-fourths of the states or by three-fourths of conventions thereof, the method of ratification being determined by Congress at the time of proposal. To date, no convention for proposing amendments has been called by the states, and only once has the convention method of ratification been employed.

Six amendments proposed by Congress have failed to be ratified by the appropriate number of states' legislatures. Four of these amendments are still technically pending before state lawmakers—the other two have expired by their own terms.