Nikolai Nikolaevich Petrov was a Russian surgeon, the founder of Russian oncology and the author of many important scientific publications. N. N. Petrov enriched the medical science with a number of valuable experimental studies, which significantly advanced the knowledge of the etiology and pathogenesis of malignant tumors. He discovered the carcinogenic effects of sunlight and the influence of photometrically established doses of ultraviolet (UV) rays on the occurrence of malignancies. He organized a laboratory of experimental cancer in Sukhumi, where one of the most important experiments on the production of malignant tumors in monkeys was carried out. He was one of the founders of the Institute of Oncology in St. Petersburg. He was an active participant in international congresses on surgery and oncology. Under his direction combined surgical and radiation treatment of malignant tumors, electrosurgery for cancer operations and treatment of wounds after removal of tumors were introduced into broad medical practice. Moreover, he was very much involved in ethical problems in surgery.