Gastroenterology was the primary focus of O. Ya. Gubergrits’ scientific activity. He was very interested in pancreatic pathology, described the pain point in the pathology of the organ’s tail, and investigated the functional condition of the pancreas in a variety of internal diseases. Numerous works are dedicated to diseases of the liver and biliary system. O. Ya. Gubergrits investigated the potential therapeutic use of non‑drug remedies, including local natural resources such as medicinal plants and mineral waters. These topics are covered in the monographs «Medicinal Plants of Udmurtia» (1958, 1969), «Medicinal Plants of Donbass» (5 editions from the 1960s to 1990), and «Mineral Waters of Udmurtia» (1954). O. Ya. Gubergrits contributed to the practical use of mineral waters by the population (he was one of the organizers of the Metallurg sanatorium in Udmurtia, studied the medicinal properties, and helped to establish serial production of the Golden Well mineral water, Donetsk region). Oleksandr Yakovich paid close attention to clinical nutrition issues. Oleksandr Yakovich spent considerable time researching the history of medicine. He examined the work of prominent clinicians such as V. P. Obraztsov, S. P. Botkin, and others. These topics were addressed in a number of his works. O. Ya. Gubergrits paid special tribute to the memory of his academic mentor, M. M. Gubergrits. Oleksandr Yakovich participated actively in the publication of «Selected Works» (Kyiv, 1959) by Maks Moiseyevich and, along with G. I. Burchinsky, published a brochure on the life and research work of the teacher. O. Ya. Gubergrits’ final monograph on the history of medicine, «V. P. Obraztsov and His School», was published after his death. More than 30 monographs, textbooks, and teaching guides, were written by Oleksandr Yakovich. Among them are «Diagnostic Value of Laboratory Studies» (1949, 1960), «Emergency Therapy for Acute Conditions in the Clinic of Internal Diseases» (1966, 1970, 1974), «Biliary Tract Diseases» (1963), «Pain in the Abdominal Cavity and Its Diagnostic Value» (1968), «Chronic Pancreatic Diseases» (1971, 1975, 1984), «Pharmacotherapy of Liver Diseases» (1971), «Prevention and Treatment Schemes for Internal Diseases» (1971), «Diseases of the Small Intestine» (1975), «Healthy Nutrition» (1977, 1985), «Clinical Gastroenterology» (1978, 1979), «Methodology of Medical Diagnosis and Prognosis» (1986), and a guide to propaedeutics of internal diseases «Direct Examination of the Patient» (1956, 1972). The latter became a real bestseller, and in 1996 was republished by professors, his followers. In 1980, O. Ya. Gubergrits received the State Prize of the Ukrainian SSR for the textbook «Internal Diseases» he co‑authored. O. Ya. Gubergrits engaged clinical personnel and practitioners actively in scientific and clinical research. Under his supervision, 54 candidate’s and 12 doctoral theses were completed, and approximately 2000 scientific papers were published.