The purpose of this paper is to discuss methods recommended and used by the Pan American Health Organization (PAHO) to monitor the interruption of indigenous measles transmission in the Region of the Americas. The methods used include house-to-house monitoring of vaccination coverage as a supervisory tool during both campaigns and routine vaccination; thoroughly investigating all measles outbreaks; performing routine surveillance, including weekly reporting from at least 80% of reporting units; and validating routine surveillance through active-case searches at health care institutions and schools and in the community. The strategies described have helped PAHO to increase the authority and accountability of vaccine program managers at the local, provincial, and national levels. Their efforts have permitted the Region of the Americas to reduce to three the number of countries with indigenous measles transmission and to reach a record low of 503 measles cases in 2001.