Rapid progress has been made from the identification of the molecular defects causing X-linked severe combined immune deficiency (X-SCID) to the development of cutting-edge therapeutic approaches such as hematopoietic stem cell transplant and gene therapy for XSCID. Successful treatment of XSCID has created a new population of patients, many of whom are now adolescents and young adults and are facing a variety of chronic problems secondary to partial correction of their underlying disease. This review focuses on the clinical challenges facing these patients (and their caregivers) and provides an overview of some of the treatment options available, including gene therapy.