Measles is the most frequent cause of vaccine-preventable childhood deaths. Infants younger than the recommended age for vaccination are susceptible to the disease, and in developing countries they have a high risk of complications and mortality. Vaccine coverage in excess of 95% interrupts endemic transmission of measles in many countries, but achievement of such coverage almost always requires coordinated supplementary mass vaccination campaigns. There are substantial health gains if countries improve measles vaccine coverage, irrespective of whether or not high coverage is achieved; these gains include much lower measles complication and case fatality rates, long-term interepidemic duration, and possibly non-specific improvements in survival of children. Investigation into the cost-effectiveness of different strategies for measles control, including mass campaigns, two-dose schedules, and young-infant doses, would help countries to formulate control policies appropriate to their setting. Pneumonia is the most common fatal complication associated with measles, and at least 50% of measles-related pneumonias are due to bacterial superinfection. WHO has developed standard case management programmes for measles, but there are several unresolved clinical issues, including optimum indications for antibiotic treatment, the importance of intravenous immunoglobulin, the role of viral coinfection, and the risk of tuberculosis after measles. The priority in worldwide efforts to control measles is to lend support to poor countries, helping them to increase vaccine coverage and sustain improvements to vaccination infrastructure, and to address technical issues with respect to optimum vaccination schedules. Measles represents a specific challenge, whereby partnerships between high-income and developing nations would reduce child mortality in developing countries; such partnerships are not without incentive for high-income countries, since without them imported measles cannot be prevented.