Theodore Kocher was awarded the Nobel Prize in 1909 for his work on the physiology, pathology and surgery of the thyroid gland. He was the first Swiss citizen and the first surgeon to ever receive such a distinction. He was a pioneer and a world leader in the surgical revolution of the end of the nineteenth century. After graduation in 1865, he traveled in Germany, England, France and Austria to observe the work of Langenbeck, Paget, Wells, Nelaton, Billroth.... In 1866, he returned to Bern and was appointed assistant in the surgical clinic of Lücke. In 1872 he applied for the succession of Lücke. After a lively debate, he was appointed by the Board of Regents against the recommendation of the faculty who wished to nominate a German surgeon, König. It proved to be a good choice, as, over a period of 45 years, Kocher developed a considerable activity in various fields of surgery leading to world-wide acclaim and renown. Kocher's most significant contribution to medicine concerned the thyroid gland. He considerably improved thyroid surgery. His anatomical knowledge, precise operating technic and respect of the aseptic principles defined by Lister, whom he had met in Glasgow, contributed to a reduction of mortality from 13% to 0.18%. He described postoperative hypothyroidism, which he called cachexia strumipriva and concluded that total thyroidectomy was not indicated in benign diseases. When he died, more than 7,000 thyroidectomies had been performed in his clinic. Kocher was also interested in orthopedics, abdominal and genitourinary surgery, surgical oncology, neurosurgery (Cushing conducted experimental research with him). He developed or modified many surgical instruments. He conducted a large number of experimental studies and published 249 articles and books.