This issue of Immunology and Allergy Clinics of North America, Guest Edited by Dr. Lisa Kobrynski, is devoted to Primary Immune Deficiencies. Articles in this issue include: Personalized therapy: Immunoglobulin replacement for antibody deficiency; Newborn Screening for Severe Combined Immunodeficiency: Update on newborn screening and lessons learned; Update on Advances in Hematopoietic Cell Transplantation for Primary Immunodeficiency Disorders; Hereditary Autoinflammatory Disorders: Recognition and treatment of inflammatory disorders of the immune system; Use of Immunomodulatory Agents to Treat Primary Immune Deficiencies: Mechanism-based therapy; Secondary Hypogammaglobulinemia: An increasingly recognized complication of treatment with immunomodulators and post-solid organ transplantation; Use of Vaccines in Primary Immunodeficiency; Gastrointestinal Manifestations and Complications of Primary Immunodeficiency Disorders; Hyper IgE Syndromes; Early Onset Inflammatory Bowel Disease; and Genome Testing to Diagnose Primary Immunodeficiency Disorders and to Identify Targeted Therapy.