This study aimed to estimate thecost-effectiveness and return on investment of HIV programsimplemented during 2003-2010 in Indonesia and to contributeto the allocative efficiency of the HIV prevention responsein Indonesia through analyses to inform the prioritizationof resources for the 2015-2019 national HIV budget in thecontext of reductions in international donor funding. Thespending-outcome relationships and epidemiological modelwere used to compare observed conditions with counterfactualscenarios of reduced/no programs to calculate hecost-effectiveness and estimate healthcare costs saved andthus the return on investment. Model simulations of epidemicprojections over many combinations of possible resourceallocations were used to identify optimal allocations forreducing new infections over the next HIV budget period.