The discovery of streptomycin is attributed to a microbiologist, Selman Waksman, Nobel Prize 1952, a paternity that was disputed by his collaborator Albert Schatz, who was the first author of the princeps article. Two pioneering clinical studies involved streptomycin, both of which have been widely used as reference works. The first one was English, under the name of Austin Bradford Hill. It inaugurated a randomization in medicine. The second trial was American, and carried out by the Veteran Administration. It made use for the first time of the "control group". The present article analyses the genesis of clinical trials and illustrates the recurrent difficulties encountered in their implementation.