In January 2007, two Phase III clinical trials of a candidate microbicide among women at high risk of HIV in India, South Africa, Benin, Uganda, and Nigeria were halted. This was done because analyses of preliminary data by the Independent Data Monitoring Committee indicated that the product was associated with an increased risk of acquiring HIV. The planning, implementation, and subsequent cessation of these trials illustrate the mechanisms for protecting participants in microbicide trials in developing countries. The closure of the trials highlights the complexities of such decisions and the range of competencies that research teams must possess.