In this paper, clinical data of 49 adult patients with agammaglobulinaemia (syn. hypogammaglobulinaemia), 15 cases of X-linked agammaglobulinaemia (XLA) and 34 of common variable immunodeficiency (CVID) are reviewed. Although immunoglobulin substitution largely abolished life-threatening respiratory tract infections, considerable infectious and non-infectious morbidity was still encountered in these patients. Almost all patients suffered from chronic or recurrent upper and lower airway infections, mainly caused by Haemophilus influenzae and pneumococci. The lower respiratory tract infections led to cumulative damage to the respiratory tract, especially in XLA patients. Also the incidence of infections outside the respiratory tract (giardiasis, Campylobacter jejuni infections) was more common in XLA patients than in CVID patients. Nodular lymphoid hyperplasia was only found in CVID. A variety of other non-infectious complications were seen especially in CVID.