350 adult patients in Sweden were included in a retrospective study covering more than 2000 patient-y, to evaluate the efficacy of immunoglobulin (Ig) prophylaxis. All patients had selective or combined IgG subclass deficiency, without IgA deficiency, and suffered from recurrent respiratory tract infections (RTIs). The patients had been given Ig prophylaxis for 0.5-21 y (mean 5.5 y). In total, 164/350 of the patients had a concomitant lung disease. Because of the heterogeneity of this retrospective material we evaluated only those patients with 4 or more antibiotic-demanding (i.e. presumably bacterial) episodes of RTI per y treated with an Ig dose of about 100 mg/kg/week (132/350). The frequency of antibiotic treated RTIs prior to and during latest y/s of Ig prophylaxis was compared. No difference in response could be found between patients with and without chronic lung diseases. In 92/132 a > or = 50% reduction of the rate of episodes of antibiotic-demanding RTIs was recorded (p < 0.001). The overall reduction of the RTI frequency was for IgG1 57%, IgG2 59%, IgG3 63% and for the combinations 61% (all p<0.001).