The most common complication of chronic lymphocytic leukaemia (CLL) is infection, which occurs mainly in advanced stages of disease or in those patients with hypogammaglobulinaemia. Intravenous immune globulin (IVIG) has been shown to be a useful prophylactic therapy against infections in such patients. A randomized, double-blind study on 36 patients receiving either 500 mg/kg or 250 mg/kg IVIG every 4 weeks was undertaken to determine the dose regimen required. There was no significant difference in the two treatment groups and we found that CLL patients were equally protected with low-dose IVIG.