Despite considerable progress in malaria control over the past decade, malaria remains a serious problem--particularly in Africa, south of the Sahara, where about 90% of clinical cases occur. Malaria, either alone or in combination with other diseases, is estimated to kill between 1.1 and 2.7 million people worldwide each year, and over 2400 million remain at risk. This report of a WHO Expert Committee reviews the progress made since 1992 in the implementation of the Global Malaria Control Strategy and analyses the effect of health sector reforms on malaria control programmes. The importance of more recent initiatives, such as the Roll Back Malaria project, is also discussed. The report focuses on disease management and on drug resistance of malaria parasites, one of the greatest challenges currently facing control programmes. Guidance is given on how to predict, prepare for, control and prevent malaria epidemics, which threaten large areas of the world. The use of chemoprophylaxis and selective vector control in the prevention of malaria is discussed. As accurate epidemiological information is essential for assessing public health needs and for monitoring malaria control programmes, a number of standardized case definitions and indicators have been developed. In order to make programme activities effective and responsive to changing epidemiological situations, the report emphasizes the need for operational research at a national level. Although existing tools have had an impact on malaria morbidity and mortality, it is clear that much remains to be done. The report concludes with a list of recommendations to ensure that the present achievements are sustained and that a greater impact is made on the disease, particularly in Africa.