This contribution focuses on the role of the firm Shimadzu in the marketing of X-ray machines in Japan during the first part of the 20th century, viewed from a business history perspective. It attempts to further understanding of the process of technology diffusion in medicine. In a global market controlled by American and German multinational enterprises, Japan appears to have been a particular country, where a domestic independent firm, Shimadzu, succeeded in establishing itself as a competitive company. This success is the result of a strategy based on both the internalisation of technological capabilities (recruitment of university graduate engineers, subcontracting of research and development activities) and an original communication policy towards the medical world. Finally, the specific structure of the Japanese medical market, composed of numerous and largely privatised small healthcare centres, facilitated the rapid diffusion of X-ray machines, a new technology which conferred a comparative advantage on its holders.