Measles is a highly communicable, acute viral illness with potential for severe complications, including death. Although endemic measles was eliminated in the United States in 2000 as a result of widespread vaccination, sporadic measles outbreaks still occur, largely associated with international travel from measles-endemic countries and pockets of unvaccinated persons (1). On August 26, 2011, the Los Angeles County Department of Public Health (LACDPH) was notified of suspected measles in a refugee from Burma who had arrived in Los Angeles, California, on August 24, after a flight from Kuala Lumpur, Malaysia. Passengers on the flight included 31 other refugees who then traveled to seven other states, widening the measles investigation and response activities (2). In California alone, 50 staff members from LACDPH and the California Department of Public Health (CDPH) interviewed and reinterviewed 298 contacts. Measles was diagnosed in three contacts of the index patient (patient A). The three contacts with measles were two passengers on the same flight as patient A and a customs worker; no secondary cases were identified. Delayed diagnosis of measles in patient A and delayed notification of health officials precluded use of measles-mumps-rubella (MMR) vaccine as an outbreak intervention. This outbreak emphasizes the importance of maintaining a high level of vaccination coverage and continued high vigilance for measles in the United States, particularly among incoming international travelers; clinicians should immediately isolate persons with suspected measles and promptly report them to health authorities.