When a medical problem is studied intensively by several investigators in the world, a solution may sometimes be found simultaneously in different countries. Seventy-five years after the discovery of insulin, the chronology of this event can be reconsidered objectively and the role of each of the protagonists evaluated. The stubbornness of Banting and Best, the technical abilities of Collip and the active support of Macleod were determinant in the use of insulin for the treatment of diabetic patients. Moreover, in the long line of experimentalists and physicians, Lancereaux and Paulesco also deserve special mention.