Malaria is a major problem in many parts of Asia, Africa, and central and South America. Malaria occurs in about 100 countries. Approximately 40 per cent of the world’s population is at risk of contracting malaria. The outlook for malaria control is grim. The disease, caused by mosquito-borne parasites, is present in 102 countries and is responsible for over 100 million clinical cases and about 2 million deaths each year. Over the past two decades, efforts to control malaria have met with less and less success. In many regions where malaria transmission had been almost eliminated, the disease has made a comeback, sometimes surpassing earlier recorded levels. The dream of completely eliminating malaria from many parts of the world, pursued with vigour during the 1950s and 1960s, has gradually faded. Few believe today that a global eradication of malaria will be possible in the foreseeable future.