Introduction An investigational 10% liquid intravenous immunoglobulin (IVIG) was studied in 63 patients with primary immunodeficiency (PID) at 15 study sites. Methods Patients were treated every 3 or 4 weeks with 254-1029 mg/kg/infusion of IVIG. Results Overall, Biotest-IVIG infusions were well tolerated. The proportion of infusions that were associated with adverse events during infusion, and up to 72 h after infusion, including those unrelated to study product, was 27.7% with an upper 95% confidence limit ≤30.6%. Two serious bacterial infections (SBIs) were observed resulting in a serious bacterial infection rate of 0.035 per person per year and an upper one-sided 99% confidence limit of ≤0.136 SBI/patient/ year. The number of days of work or school missed due to infection were relatively low at 2.28 days/patient/year.Two patients were hospitalized for infection producing a rate of 0.21 hospitalization days/patient/year. The IgG half-life was approximately 30 days with variation among individuals. Conclusions Pharmacokinetic parameters of specific antibody activities were essentially the same as those of total IgG. Biotest-IVIG is safe and effective in the treatment of PID. © The Author(s) 2012.