Sporadic importations of measles into the United States have occurred since the disease was declared eliminated from the United States in 2000. During January-July 2008, 131 measles cases were reported to CDC, compared with an average of 63 cases per year during 2000-2007. This report updates an earlier report on measles in the United States during 2008 and summarizes two recent U.S outbreaks among unvaccinated school-aged children. Among those measles cases reported during the first 7 months of 2008, 76% were in persons aged <20 years, and 91% were in persons who were unvaccinated or of unknown vaccination status. Of the 131 cases, 89% were imported from or associated with importations from other countries, particularly countries in Europe, where several outbreaks are ongoing. The findings demonstrate that measles outbreaks can occur in communities with a high number of unvaccinated persons and that maintaining high overall measles, mumps, and rubella (MMR) vaccination coverage rates in the United States is needed to continue to limit the spread of measles.