In 1885, Daniel Carrion (1857-1885), a young Peruvian medical student, was trying to establish the prodromal symptoms of 'verruga disease', an infectious disease rare outside South America but endemic in parts of Peru. As part of this investigation he was inoculated with fluid from a verruga lesion from a patient with the chronic form of the disease. He recorded the clinical features which developed, including fever, malaise, arthralgia, vomiting and anaemia, and it became apparent that he had developed the anaemic, febrile, acute phase of the illness (known as Oroya fever). This did not however progress in his case to the chronic form of the disease, and he died a few weeks later on 5 October 1885. His sacrifice served to establish, supposedly, that Oroya fever and verruga disease had a common aetiology and his death stimulated further research into the cause, now established as the bacterium Bartonella bacilliformis. Carrion is considered a martyr of Peruvian medicine and 5 October has been designated Peruvian Medicine Day in his honour. © 2012 Royal College of Physicians of Edinburgh.