PURPOSE: The previous studies with Flebogamma(®) 5 % DIF intravenous immunoglobulin (IVIG) contained insufficient numbers of pediatric subjects to fully warrant a pediatric indication by the FDA. The objective of this study was to evaluate the efficacy, safety, and pharmacokinetics of Flebogamma® 5 % DIF for replacement therapy in children (age 2-16) with primary immunodeficiency diseases (PIDD). METHODS: IVIG was administered at eight clinical sites to 24 subjects with well-defined PIDD at a dose of 300-800 mg/kg every 21-28 days for 12 months. The pharmacokinetics endpoint in this study was the dose-adjusted increment of the serum IgG trough levels. RESULTS: The calculated serious bacterial infection rate was 0.05/subject/year. The incidence of adverse events considered potentially related to IVIG during or within 72 h after completing an infusion was within the FDA guidance threshold of <40 % at each time point. Dose-adjusted incremental IgG levels remained approximately equal to or slightly greater than pre-study IgG levels (between 800 and 1000 mg/dL throughout) when the subjects were treated with IVIG therapy other than Flebogamma(®) DIF 5 % indicating no evidence of a different pharmacokinetic profile in this pediatric population if compared to those profiles in previous Flebogamma studies in predominately adult populations. CONCLUSIONS: Flebogamma(®) 5 % DIF is efficacious and safe, has adequate pharmacokinetic properties, is well-tolerated, and maintains the profile of Flebogamma(®) 5 % for the treatment of children with primary humoral immunodeficiency diseases.