Clinical trials are usually designed to meet registration requirements in developed countries, and do not always address key concerns for use in developing countries. Four late-stage investigational new drugs - rilpivirine, etravirine, raltegravir and maraviroc - show potential to improve antiretroviral therapy. However, a number of issues could limit their use in developing countries, including dose selection, treatment strategy, combination with other drugs, use in specific populations and reliance on expensive tests. Key research questions relevant for developing countries need to be answered early in the drug development process to ensure maximum benefit for the majority.