There are an estimated 234,000 cases of measles and 13,851 measles-related deaths per year in Mali. In 1998 and 1999, 548,309 children aged 9-59 months were vaccinated against measles during mass campaigns in urban centers across Mali. After the first campaign, measles incidence decreased by 95% in districts encompassing vaccinated urban centers and by 41% in nonvaccinated districts. There was no shift in the proportion of cases by age group in vaccinated centers. Measles in vaccinated districts after the campaign was likely related to persistent transmission in age groups not targeted for vaccination and among children living in nonvaccinated districts. The second campaign (1999) did not change the incidence of measles in vaccinated compared with nonvaccinated centers. Urban mass measles vaccination probably did not affect overall measles transmission in Mali. Mass vaccination of all children in Mali, targeting a larger age group, will be necessary to reach measles control objectives.