The Spanish patent system in the twentieth century has been defined by the incorporation of technologies and regulations. Patents have been intermediaries, and their regulation has been subject to complaints, some of which came from abroad. To analyse this reality, I propose two case studies that suggest different patent cultures, subject to specific times and places. The first case, the arrival in Spain of the first North American patents to protect production of penicillins, shows the mediation role patents played. Patents connected practices, languages, and interests from different Spanish and North American professional communities – clinical, industrial, and political – at the end of the 1940s and beginning of the 1950s. The second case, the launch on the market of a Spanish patent for a DNA polymerase, product of research done in a Spanish laboratory and patented in the USA in 1988, shows rather local regulations and the limits on international harmonization. The political, social, and economic changes that protection systems demand differ from one place to another, and do not always coincide with voices calling for harmonization.