Background and Design.- Infections are res¬ponsible from the majority of disease-related de¬aths in patients with chronic lymphocytic leukemia (CLL). Hy'pogammaglobulinemia is the most impor¬tant cause of increased susceptibility to infections in this disease. Intravenous immunoglobulin (IVIG) is becoming an important adjunct to the prophyla¬xis and therapy of infections in CLL. Five patients with Rai stage III-IV CLL, and with frequent and se¬vere infections, who where treated with 3 courses of IVIG (300 mg/kg, every three weeks.) prophylac-tically are presented. Results.- IgG levels increased in all patients af¬ter IVIG treatment. No infections were observed during treatment and in the follow-up period, ex¬cept one episode of infection in öne patient. Conclusion.- IVIG treatment is effective in re¬ducing the frequency of infections in CLL; but, regarding the expense of the therapy, it should be reserved for selected patients who develop frequ¬ent, severe and life-threatening infections.