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Over the past century, tropical medicine has passed through several overlapping phases. Initially, the picture was of endemic and epidemic diseases that wreaked havoc on people living in warm climates and visitors to these areas. High morbidity and mortality associated with these diseases reflected the poor state of knowledge about their causes and epidemiology and the lack of effective technologies for their control. At this stage, tropical medicine was dominated by parasitic and infectious diseases that had affinity for warm climates and some specific nutritional disorders. The next phase involved the steady accumulation of knowledge about the aetiological agents and, in the case of parasitic and infectious diseases, identification of reservoirs and vectors. The development of new and improved technologies for the control of tropical diseases characterised the third phase. The new products included drugs, diagnostic tools, vector control measures and vaccines. In the fourth phase, the new technologies are being deployed in programmes aimed at achieving disease control and, where feasible, total elimination of the problem. In the course of these operations, many useful lessons have been learnt from both the successes and failures of major schemes. In particular, experience has shown the important role of research not only in providing new technologies but also in optimising their effectiveness when applied in control programmes. The role of social and behavioural factors in the epidemiology and control of tropical diseases has drawn attention to the value of a multidisciplinary approach in designing and implementing control programmes. There is a sense of cautious optimism that, if the lessons learnt over the past century are carefully applied, further gains can be made in controlling and eliminating the classical problems that characterised tropical medicine at the beginning of this century.