The purpose of this protocol is to study patients with primary immunodeficiency disorders with the goal of contributing to both the clinical and molecular understanding of this heterogeneous group of inherited diseases. Clinical issues to be addressed will include disease manifestations and evolution, as well prevention and management of medical problems. Patients with diseases of known molecular basis (including Wiskott-Aldrich syndrome, ADA deficiency, JAK3 deficiency and other syndromes) will be genotyped in order to investigate phenotype-genotype correlation. Patients with disease of unknown or incomplete genetic characterization will be studied with hopes of contributing to the identification of specific genes responsible for disease. Studies of fresh cells, cell lines and tissue samples will be performed to help characterize the patient s syndrome as well as to test the efficacy of genetic correction when available.