With the large majority of incident and prevalent HIV infections in low- and middle-income countries, we have an imperative to address the epidemic where it is occurring;moreover, the high incidence seen in some countries lends itself to evaluating prevention interventions in ways that efficacy can be measured. The roll-out of these programs has led to unique opportunities for research, technical assistance, and training. The Global Response Core, formerly the International Core, facilitates multidisciplinary HIV research in low- and middle-income countries, supports systematic literature reviews, and supports implementation of evidence-based prevention interventions. We build linkages and ensure integration among CAPS and other UCSF AIDS and global health researchers and educators as well as with our national and international collaborators and institutions (see Appendix 8.1). The core supports the work of core and affiliated faculty conducting HIV research, training programs to build capacity for a global response, and technical assistance.