Arachu Castro is Assistant Professor of Social Medicine in the Department of Social Medicine at Harvard Medical School in Boston and Director of the Institute for Health and Social Justice at Partners in Health. She has taught at the University of Barcelona and the National School of Public Health in Spain, at the National University at Cordoba, Argentina, and at the Institute of Tropical Medicine in Havana, Cuba. Merrill Singer is Associate Director and Chief of Research at the Hispanic Health Council in Hartford, Connecticut, as well as Assistant Clinical Professor at the University of Connecticut Medical School and a member of the Executive Committee of the Center for Interdisciplinary Research on AIDS at the Yale University School of Public Health.