During the twentieth century, spectacular developments in science, technology and medical practice coupled with economic growth have transformed health care and improved the lives of many people. Despite such progress, the world today is more inequitable than it was 50 years ago: disparities in wealth and health are widening inexorably, and infectious diseases are again becoming a major scourge and pose a threat to the lives of all. Hundreds of millions of people live in degrading poverty, with little, if any, access to health care. Recognition of this context in which much research takes place should sharpen our focus on the ethical requirements for research that could improve the health of a greater proportion of the world's population--one of the most pressing moral problems of our time. The intense debate on ethical dilemmas associated with an expanding programme of clinical research in developing countries has revealed much common ground, but has also left a residuum of controversy. We suggest that contested issues could be resolved by paying greater attention to different world views on the relationship between research and clinical care and by defining policies that both progressively improve the standard of care in research and link research to improved delivery of health care in developing countries.