Octagam is an intravenous immunoglobulin preparation registered in Europe for treating primary immunodeficiency diseases (PID). The present clinical trial was designed to demonstrate that Octagam meets the minimal efficacy requirement of the U.S. Food and Drug Administration-that treatment should result in </=1 serious infection/subject/year. The objectives of this clinical trial were to show that Octagam meets this requirement, and to confirm the safety of Octagam. Forty-six subjects with well-defined PID received Octagam (either 400-600 mg/kg every 28 days or 300-450 mg/kg every 21 days) for 12 months. The primary efficacy variable was the number of serious infections/subject/year. The estimated infection rate was 0.1 serious infections/subject/year. The half-life ( T (1/2)) of total IgG was 41 days. Adverse events potentially related to Octagam occurred in 5% of infusions, either during or within 30 min of the procedure. Octagam meets the Food and Drug Administration minimal requirement for efficacy. In addition, Octagam had a T (1/2) (IgG) comparable with published data, and was well tolerated. Octagam treatment is safe and resulted in 0.1 serious infections/subject/year in primary immunodeficient subjects.