ArgumentUsing the example of the anti-tuberculosis vaccine BCG during the 1920s and 1930s, this article asks how a labile laboratory-modified bacteria was transformed into a genuine standard vaccine packaged and commercialized as a pharmaceutical product. At the center of the analysis lies the notion of standardization inquiring why and how a local laboratory process with standard operating procedures reached its limits and was transformed when the product faced international distribution. Moving from Paul Ehrlich's initial technological notion ofWertbestimmungreferring to a practice (...) physiologically testing the effects of ill-defined antitoxins, the concept of standardization is extended to pharmaceutical and economical meanings implying quality control for biological therapeutic agents produced by a variety of industrial entrepreneurs. Following the request for product uniformity, two ways to maintain levels of compatibility and commonality are depicted opposing SOPs and end-product control. Furthermore, standardization is understood as a spiral, never ending process where progressive transformation of the vaccine in its production and medical uses periodically recreated the necessity of standardization. Developments analyzed are thus understood as a stabilization process aligning laboratory settings, products, and practices with medical theories and practices through technical, bureaucratic, and organizational systems. A paradox of the analysis is that standardization as a historical phenomenon and moment in the history of drug development was initially linked to a problem of under-determination of what was to be standardized and to a knowledge gap before it could become a central concept for quality control. (shrink)