Background: Chronic granulomatous disease (CGD) is a genetic disorder. People with CGD are missing a gene that affects their white blood cells. White cells are part of the immune system, and people with GCD are vulnerable to many infections. Researchers want to test a new treatment to replace the missing gene that may be safer than the current treatment for CGD. Objective: To test a new type of gene therapy in people with CGD. Eligibility: People aged 3 years or older with CGD. Design: Participants will undergo apheresis: Blood will be collected through a tube attached to a needle inserted in a vein; the blood will run through a machine that separates certain cells (stem cells); the remaining blood will be returned to the body through a second needle. The participant s stem cells will be modified in a laboratory to add the gene they are missing. Participants will stay in the hospital for about 40 days. For the first 10 days, they will undergo many exams, including imaging scans and tests of their heart and lung function. They will receive drugs to prepare their bodies for the gene therapy. They will receive a "central line": A hollow tube will be inserted into a vein in the chest, with a port opening above the skin. This port will be used to draw blood and administer drugs without the need for new needle sticks. For the gene therapy, each participant s own modified stem cells will be put into their body through the port. Participants will have 8 follow-up visits over 3 years.