The purpose of this section of the monograph is to familiarize readers with the role of programmed cell death type 1—apoptosis in autoimmune destruction of the pancreas in type 1 diabetes mellitus (T1DM-1). The task of focusing the reader’s attention on the mechanisms of pancreatic b-cells apoptosis is explained by the fact that the interest of scientists in this problem continues to grow. Sections of the chapter are devoted to the modern concept of T1DM-1 immunopathogenesis, the role of insufficient apoptosis of circulating effector T cells, on the one hand, and enhanced apoptosis of b-cells, on the other hand. Special attention is paid to the prospects for the treatment and prevention of T1DM. The chapter presents the results of experimental studies on the role of apoptosis in the immunopathogenesis of T1DM. Separately, the results of the authors’ own studies are considered. The chapter was based on sources from international data bases: Scopus, Springer, PubMed. The authors express the hope that the chapter will contribute not only to a deeper understanding of the pathogenesis of T1DM, but also to arouse interest in the prospects for the treatment and prevention of this disease. The chapter is intended for students of medical universities and a wide range of readers with higher medical and biological education.