Time course of Marburg virus (strain Popp) accumulation and changes in hematological parameters were studied in aerosol infected M.rhesus monkeys. The lungs were the first organ in which the virus was detected after respiratory infection of monkeys. Four days after inoculation the virus was detected in the liver, spleen, blood, and thymus. Six days after inoculation the virus was present in virtually all organs and secretions. The period of fever was associated with manifest leukopenia in primates. Blood clotting time drastically increased by the moment of animal death.