This is a prospective, single blind, randomized, multi-center cross-over trial in patients with Primary Immune Deficiency. Patients with a confirmed diagnosis of primary Immune Deficiency will be treated with two daily infusions given 3-4 weeks apart at the fixed individual IGIV dose regimen (400-600 mg/kg) established prior to entry into the study. Any subject with an established dose in the range of 200-399 mg/kg will be assigned to receive 400 mg/kg during the course of the study during the same dosing schedule established prior to entry into the study.