This paper analyzes the politics of intellectual property (IP) and public health in Brazil and Mexico. Both countries introduced pharmaceutical patents in the 1990s, to comply with their international obligations. Indeed, both countries’ IP systems were markedly similar in being favorable to the interests of the transnational, innovation-based pharmaceutical sector. Yet since the late 1990s the two countries have diverged in dramatic fashion. In Brazil the response to the high price of drugs and societal demands to reform the IP system has been to make obtaining private ownership over knowledge more difficult and to increase the rights of third parties to access and use knowledge. In Mexico, the response to similar demands has been to raise impediments to third parties’ rights of access and use and effectively extend the periods of protection granted to patent-owners. To explain these differences the paper adopts a political economy approach, analyzing the nature of actors pushing for IP reform and subsequent patterns of alliance formation and political mobilization. In both countries, drug patents, escalating prices, and limited access led to backlash against the IP system, but the two countries demonstrate marked variation in the presence of powerful alliance partners to lend their support to activists clamoring for change. In Brazil, the combination of a strong, interested, and active Ministry of Health and a more autonomous local pharmaceutical sector created a propitious environment for initiatives to reform the IP system. In Mexico, the subordination of the Secretariat of Health and fundamental transformations of the local industrial sector meant that calls to reform the IP system were not well-received. Instead, the reform project in Mexico became commandeered by IP owners and ultimately had the perverse effect of reinforcing and strengthening the system that was being challenged. The paper concludes by underscoring the importance of pharmaceutical industries for development. The findings suggest that the existence of independent pharmaceutical sectors may not just be beneficial for industrial development, but also for promoting public health and pursuing humanitarian goals. The basis of this conclusion is that the key variable in explaining efforts to reform patent systems to increase access to drugs is the presence of an autonomous, national pharmaceutical industry that is available as an alliance partner for those pushing for such reforms. Thus, the key to IP-for-humanitarianism is maintenance of some degree of IP-for-industrialization.