Injecting drug users (IDU) are a hard-to-reach population. The treatment objectives are to reduce their risk factors, to guide them to total abstinence or to antagonist treatment. When IDU are not ready for detoxification, they are referred to Syringe Exchange Programs (SEP). The objective of SEP is harm reduction of blood-borne viruses (of HIV, HBV, HCV). The authors aimed to define the issues related to harm reduction, to discuss the results of SEP in the world, and to describe our experience. We analyzed the world literature and our experience. In this article, we describe the rehabilitation school of thought (which supports complete drug abstinence), the harm reduction school of thought (which refers to drug addiction as a chronic disease), and the possible continuum between these two schools of thought. The AIDS pandemic and the epidemiology of world drug addiction by injection are described, together with the principles of SEP and their evaluation in the world. In addition, we describe drug use in Israel and HIV infection among IDU. Finally, we analyze our preliminary results of the SEP pilot in Israel, during the years 2004-2005, and included 462 IDUs. In conclusion, considering the difficulties that exist with IDUs, most articles emphasize the importance of SEP in this population while sometimes also expressing its effectiveness in preventing transmissions of blood-borne viruses. In Israel, a pilot project has existed since the end of 2003, and has expanded progressively to three cities. An overall evaluation of this program is under preparation.