Immunodeficiency often has a genetic basis. Immune defects are the predominant manifestation in primary immunodeficiency disorders, and immune defects may also be associated with a number of other recognizable syndromes. There are 45 recognized primary immunodeficiency disorders, but immunodeficiency has been reported in 105 other syndromes. Abnormalities associated with these syndromes include growth deficiency (19 syndromes with disproportionate or proportionate short stature); specific organ system dysfunction (39 with gastrointestinal, dermatologic, or neurologic abnormalities); inborn errors of metabolism (17); miscellaneous anomalies (17); and chromosome anomalies (13). In most of these disorders, immunodeficiency is present in only a portion of the patients. However, in 49 syndromes, immunodeficiency is present in the vast majority. We review the clinical manifestations of each syndrome and delineate the associated immune defects. For most, the underlying mechanism linking the immune defect and other anomalies is unclear. Recognition of these conditions involving both the immune and other organ systems may facilitate accurate diagnosis and management, as well as yield information regarding genes critical for the development of the involved systems.