BACKGROUND: The occurrence of respiratory tract viral infections in patients with primary hypogammaglobulinemia has not been studied. OBJECTIVE: We conducted a prospective 12-month follow-up study of respiratory tract infections in 12 adult patients with primary hypogammaglobulinemia. METHODS: Nasal swab samples and induced sputum samples were taken at the onset of acute respiratory tract infection and every 3 months thereafter. Samples were tested for bacteria and viruses. PCR tests were performed for 15 respiratory tract viruses. In case the results for rhinovirus were positive, follow-up nasal swab samples were taken every 2 weeks until rhinoviral PCR results became negative. Patients completed symptom diaries, which were collected every month. The spouses of the patients served as healthy control subjects. RESULTS: During the 12-month period, the 12 patients had 65 episodes of acute respiratory tract infections, and the 11 spouses had 12 acute episodes (P < .001). Respiratory tract viruses were found in sputum in 54% of the infections. Rhinovirus was the most common virus. In more than half of our patients, rhinoviral PCR results stayed positive for more than 2 months. The most long-acting persistence with the same rhinovirus was 4 months. CONCLUSIONS: Despite adequate immunoglobulin replacement therapy, patients with primary hypogammaglobulinemia have increased susceptibility to respiratory tract viral infections. Rhinoviral infections are frequent and prolonged.