The chapter describes experiments performed by Bernard B. Brodie and Julius Axelrod in an article published in 1948 and entitled ‘The fate of acetanilide in man’. This was an important breakthrough in the history of paracetamol (acetaminophen), which was synthesized in 1878 but only clinically used in 1955. We highlight how this article historically catalysed the rehabilitation (also called ‘the rediscovery’) of this popular over-the-counter painkiller. Demonstrating that paracetamol was the key active metabolite of acetanilide (an antipyretic/analgesic used at that time), and discarding the false idea that paracetamol causes methaemoglobinaemia, Brodie and Axelrod paved the way for this molecule to become nowadays the most sold analgesic worldwide, one which is still the subject of scientific publications.