The possibility of emergency prophylaxis of Marburg hemorrhagic fever with leukocytic and recombinant interferons was studied in experiments on Cercopithecus aethiops. None of the agents protected monkeys from the action of lethal doses of Marburg virus. Recombinant interferon-alpha(2)administered according to the emergency prophylaxis schedule prolonged the mean life-span of monkeys injected with Marburg virus in doses of 100 and 1000 LD50 by 1.9 and 6.1 days, respectively.