We made clinical and immunologic observations of 30 children with common variable hypogammaglobulinemia. The mean age at diagnosis was 10.5 years, five years after clinical onset. Diagnosis was initially made based on a history of recurrent otobronchopulmonary infections, diarrhea, or both. The most common complications included short stature, bronchiectasis, and malabsorption, often associated with giardiasis or sprue. Nine patients had associated autoimmune diseases (eg, atrophic gastritis, arthritis, and hemolytic anemia). Three patients died, one of chronic respiratory insufficiency, one of chronic persisting hepatitis, and one of osteogenic sarcoma. Humoral and cellular immune functions of all patients were examined.