To obtain hyperimmune serum appropriate for the treatment of filovirus infection, methods were developed to immunize nonsusceptible animals with live Ebola (EBO) virus preparations. Immune plasma with high ELISA and neutralization-specific antibody titers was obtained by multiple immunization of sheep and goats with preparations of live EBO virus. Goat immunoglobulin was prepared by Cohn's method and tested on guinea pigs, using an EBO virus strain that is highly pathogenic for guinea pigs. Prophylaxis with these immunoglobulins within 48 h after infection was effective in challenge experiments, with a log10 prophylaxis index as high as 1.92+/-0.52. Other studies have shown that equine anti-EBO virus immunoglobulins worked well in baboons. The goat immunoglobulins were also tested in preclinical trials on laboratory animals; after being positively evaluated, they were administered to volunteers in clinical trials for biologic safety and reactivity, and they were administered to researchers suspected of becoming infected with EBO during their experimental work. These immunoglobulins may be useful for the emergency treatment of persons accidentally infected with EBO.