Technological advances in diagnostics and therapeutics have the potential to revolutionize health care and improve the lives of millions of people. However, many of these technologies remain out of reach for those who need them, particularly the poor in low- and middle-income countries. The reasons for this inaccessibility vary, depending on the disease at issue and whether it is also endemic in affluent countries, the quality and availability of local healthcare services, and the type of technology and its current stage of development. To be effective, strategies to improve the accessibility of a treatment must address the particular reasons for its inaccessibility.