This paper examines the patterns of knowledge flow from European Union countries, Japan and the United States to a selection of emerging countries from Latin America and Asia in the pharmaceutical industry, using patent citation as an indicator. A knowledge diffusion model was estimated with data based on USPTO patents granted to resident and non-resident holders in this technological field. Technological proximity of Latin American and Asian countries vis-à-vis the United States was found to be lower due to the fact that the quantity of citable patents is much greater than that coming from the European Union and Japan. Even though geographically Mexico is the closest country to the Available online at www.sciencedirect.com www.cya.unam.mx/index.php/cya Contaduría y Administración 60 (S1) 31-56