Marburg virus (strain Popp) was found to accumulate in various organs of guinea pigs after aerogenic infection. At the initial stage of the infection primary multiplication of the virus took place in the lungs. The presence of the virus in bronchopulmonary washings 2-3 days after infection, leukopenia and hyperthermia 4 days after infection are the earliest virological and clinical signs of disease in aerogenically infected guinea pigs.