The present article aims at contextualizing the first Brazilian experience with compulsory licensing, which functions as a defense mechanism to prevent excessive pricing by holders of patents. According to this mechanism, a government can authorize a third party to explore the patented object (in this case a drug) without previous consent from the patent holder. On May 4, 2007, Brazil officially issued compulsory licensing of the antiretroviral drug efavirenz for public, non-commercial use. Initially, generic versions of the drug were purchased from laboratories in India. The next step was the manufacture of efavirenz by Farmanguinhos, official pharmaceutical laboratory (Fundação Osvaldo Cruz). It is concluded that the decision made by the Brazilian government to issue compulsory licensing of efavirenz was correct, taking into account the projected savings of US$ 236.8 until 2012 and the guarantee of availability of efavirenz, the most usual free antiretroviral treatment provided in Brazil.