Aims: Since the Nobel Prize in Physiology or Medicine was awarded in 1923 to FG Banting and JJR Macleod, many voices have been raised against this decision. The bitterest protest was that of the Romanian scientist Nicolae C. Paulescu. In 2002, The Romanian Academy of Sciences, the European Association for the Study of Diabetes (EASD) and the International Diabetes Federation (IDF) planned to hold a series of academic events the following year in Paris to acknowledge Paulescu's scientific merits in the discovery of the antidiabetic hormone. However, the initiative was cancelled in August 2003, when the European Center of the Simon Wiesenthal Foundation (SWC) accused Paulescu of being antisemitic. The authors of this manuscript have decided to approach "the Paulescu case" from its double aspect, scientific and sociopolitical, to analyze the circumstances surrounding the discovery of the antidiabetic hormone, and Paulescu's alleged antisemitic past in the historical context of the Romanian nation in the interwar period., Methods: We contacted the SWC and people related to the 2003 events in Paris. We performed a comparative review of the documents published by the Toronto group and by Paulescu and analyzed the correspondence and articles generated by international experts from the scientific community interested in the controversy. We carried out an exhaustive bibliographic search through several online catalogs (INDEXCAT, NLM Gateway, EUREKA, MEDHIST). We travelled to Bucharest, where we visited Paulescu's house-museum, interviewed a former student of the Romanian professor, and a prominent medical historian who was knowledgeable about Paulescu's scientific and political biography. Dan Angelescu†, son of Dr. Constantin Angelescu (1904-1990), Paulescu's nephew and collaborator, provided us with a copy of all the available documentation from Paulescu's personal archive. It constitutes an essential source for understanding Paulescu's personal, political and academic biography. Archives consulted: Românǎ Academy (Bucharest). Personal Archive of Paulescu, House -Museum (Bucharest)*. Romanian Jewish Heritage (Bucharest). http://romanianjewish.org/ **. Simon Wiesenthal Center (Los Angeles, CA) http://www.wiesenthal.com **. Romanian Patent Office. Oficiul de Stat pentru Invenții şi Mǎrci (OSIM) (Bucharest)***. Nobel Archives (Stockholm) https://www.nobelprize.org . Internet Archive (San Francisco, CA) https://archive.org **. Wellcome Library (London) https://wellcomelibrary.org **. The European Library https://www.theeuropeanlibrary.org/ **. US National Library of Medicine, NLM historical collections http://www.nlm.nih.gov/hmd/index.html **. US. Holocaust Memorial Museum http://www.ushmm.org/ (*: archive consulted on site; **: material found in the online catalog of the archive; ***: archivists sent us digitized copies of archival material). Books consulted for information on the history of Romania and antisemitism: "Nationalist ideology and antisemitism. The case of Romanian intellectuals in the 1930s", by Leon Volovici; "The mystique of ultranationalism: History of the Iron Guard, Romania, 1919-1941" by Francisco Vega; "Romania 1866-1947", by Keith Hitchins; "History of Romania. Compendium", by Ioan-Aurel Pop and Joan Bolovan; "The Holocaust in Romania. The destruction of Jews and Gypsies under the Antonescu regime, 1940-1944", by Radu Ioanid; "The Jews of East Central Europe between the World Wars", by Ezra Mendelson; "Cultural Politics in Greater Romania. Regionalism, Nation Building and Ethnic Struggle, 1918-1930", by Irina Livezeanu, and "Judeophobia. How and when it is born, where and why it survives", by Gustavo Daniel Perednik. Articles are referenced in the bibliography section at the end of the manuscript., Results: A-Nicolae Paulescu developed an intense long-term research activity, which included complete pancreatectomy and preparation of a pancreatic extract (PE) containing the antidiabetic hormone he called pancreina. Parenteral administration of the PE achieved excellent results in the treatment of experimental diabetes in dogs and induction of hypoglycemia in the healthy animal. This work was initiated before 1916 and published at least eight months antedating the publication of the first article by Banting and Best (February 1922), who were acquainted with Paulescu's results, but misinterpreted them. The pancreatic extract of the two Canadian researchers, -iletin/insulin-, only achieved similar results to that of the Romanian scientist once they abandoned the use of the "degenerated pancreas" extract (ligation of the ductal system), replacing it with the pancreas of adult or fetal bovine. Pancreina and insulin were very similar. The award of the Nobel Prize in Physiology or Medicine to FG Banting and JJR Macleod in October 1923 honored the successful clinical use of insulin in patients with diabetes mellitus. Paulescu's achievements were ignored. B-Nicolae Paulescu publicly manifested his Judeophobic ideology on multiple occasions in academic and political interventions and in publications and participated with other figures from the Romanian intellectual sphere in the founding of the Uniunea Național Crestinǎ (UNC, National Christian Union) in 1922 and of the Liga Apǎrǎrii Național Cresține (LANC, League for Christian National Defense) in 1923, antisemitic far-right political parties, associated with an irrational Christian orthodoxy and hatred of Jews. Paulescu played a pivotal role in the spread of antisemitism., Conclusions: A-The Romanian scientist NC Paulescu started an intense research program aimed at the isolation of the antidiabetic hormone before 1916, including an original procedure of pancreatectomy in the dog and the elaboration of a pancreatic extract that achieved excellent results in the treatment of experimental diabetes, demonstrating its beneficial effects on the metabolism of carbohydrates, proteins and fats and reducing both glycosuria and glycemia and the urinary excretion of ketone bodies of depancreatized dogs toward normality. The results of these investigations were published in 1920 and 1921, predating the first report published by FG Banting and CH Best in February 1922. It has been sufficiently demonstrated that Canadian researchers were aware of Paulescu's excellent results, mentioning them only in passing, albeit erroneously misrepresenting key results of the Romanian scientist's publication in the aforementioned seminal Canadian article. Expert historians and international scientists have recognized that the pancreatic extract that Paulescu called pancreina and that obtained by Banting and Best, insulin, were very similar. The October 1923 award of the Nobel Prize in Physiology or Medicine to FG Banting and JJR Macleod ignored Paulescu's scientific achievements in the treatment of experimental diabetes and rewarded the extraordinary advance of insulin treatment in human diabetes. B-At the end of August 2003, a few days before the date of the celebration at the Hôtel Dieu in Paris of the scheduled program of tribute to the scientific merits of NC Paulescu and his important contribution to the discovery of the antidiabetic hormone, convened by the Romanian Academy and the International Diabetes Federation, the Wiesenthal Foundation publicly accused the Romanian scientist of being an antisemite, an act that determined the cancellation of the announced events. The exhaustive investigation of the personal convictions and antisemitic behavior of Nicolae C. Paulescu has undoubtedly documented the Judeophobic ideology of the Romanian scientist, linked to his orthodox religious radicalism, manifested in multiple documents (mostly pamphlets) and interventions in collaboration with other relevant personalities of the Romanian intelligentsia of his time. Furthermore, Paulescu participated in the creation of political organizations of the most radical extreme right that played a fundamental role in the spread of antisemitism amongst the Romanian population and the university community., (© 2023. The Author(s).)