Inhalational anthrax infection is associated with a 60-100% mortality rate, depending on the rapidity with which appropriate antimicrobial therapy is initiated. Experiments using an animal model of inhalational anthrax suggest that adjunctive therapy with equine-derived anti-anthrax antisera may be associated with higher survival rates, however no human-derived antisera are currently available. The purpose of this protocol is to provide a mechanism for obtaining high-titer anti-anthrax immunoglobulin by plasmapheresis of human volunteers who have recently received a course of anthrax vaccination. Volunteers are Department of Defense (DoD) employees and military personnel who are within 3 to 12 weeks of having received a fourth or greater dose of AVA if four to six total inoculations were given, or within 6 months of the last dose if seven or more AVA inoculations were given. All vaccinees were vaccinated as a requirement of their tour of duty and will otherwise meet all blood donor eligibility criteria, in accord with Food and Drug Administration (FDA) requirements and American Association of Blood Banks (AABB) standards. Plasmapheresis will be accomplished using licensed apheresis devices and standard collection techniques, and products will meet all blood safety testing requirements currently mandated by the FDA. Plasma components collected under this protocol will be stored in the frozen state as fresh frozen plasma (FFP) until a protocol for administration of these components to human patients critically ill with inhalational anthrax infection has been reviewed and approved by the IRB's of NIH, CDC, and USAMRIID. Following this approval, products will undergo standard Cohn-Oncley fractionation into a concentrated immunoglobulin preparation suitable for intravenous use, to be designated anthrax immune globulin intravenous (AIGIV). Intravenous administration of products derived from plasma collected under this protocol, whether as single-donor FFP or as AIGIV, will occur under a Phase I/II trial involving an Investigational New Drug (IND) exemption, with the IND held by the Centers for Disease Control and Prevention (CDC). The plasma products collected under this protocol will also be used in pharmacokinetic, dose finding, and efficacy studies in animals, and to establish a repository of reference serum standards at the CDC. This study represents a collaborative effort between the DTM/NIH, CDC, and DoD.