Intravenous immunoglobulin (IVIg) is accepted as an effective and well-tolerated treatment for primary and secondary immunodeficiencies (ID) and immune thrombocytopenia (ITP). Adverse reactions of IVIg are usually mild, comprising transient flu-like symptoms, change in blood pressure and tachycardia. However IVIg therapy can be burdensome for both patients and healthcare facilities, since the infusion may take up to 4 h to administer. The objective of our multicentre, prospective, open-label phase III trial was to evaluate the tolerability and safety of human normal immunoglobulin 50 g/l (Ig VENA) at high intravenous infusion rates in adult patients with ID and ITP who had previously tolerated IVIg treatment, by progressively increasing infusion rate up to 8 ml/kg/hr. 39 ID patients received three infusions, 5 ITP patients received up to a maximum of 5 infusions for a maximum of 5 days. Overall 55 adverse events were reported in 18 patients, and all were mild and self-limiting. Two serious adverse events occurred in ID patients and 1 in an ITP patient; none was fatal or treatment-related. No clinically significant changes or abnormalities were observed in vital signs, laboratory results and HRQoL. In summary, in this study, more rapid IVIg infusions were well tolerated by ID and ITP patients, while maintaining their quality of life, helping to minimise the time spent in outpatient hospital visiting to potentially optimise adherence to treatment.