Primary immune deficiencies (PID), or more recently, inborn errors of immunity (IEI), resulting from genetic defects of the immune system may present with increased sus-ceptibility to infections, persistent inflammation, and autoimmunity. With recent in-troduction of next generation sequencing, the number of IEIs increases rapidly, reaching to 484 in 2022. Hematopoietic stem cell transplantation (HSCT) has been used over decades as a mainstay of specific treatment modality, while gene therapy and pharmacologic approach have been attempted with promising results in some PID in recent years. The survival following allogeneic HSCT for PID is now generally ＞80%. The indication and timing of transplant must be individualized not only on the basis of the specific PID but also on the characteristics of the individual patient. For the successful transplant outcome, the choice of donor and the optimal pretrans-plant conditioning regimen is important. This article will discuss current status and recommendations from specialists in HSCT for some representative PID, including severe combined immunodeficiency (SCID), CD40 ligand or CD40 deficiency, Wiskott-Aldrich syndrome, hemophagocytic lymphohistiocytosis, and chronic gran-ulomatous disease, along with our personal experience of PID treatm...