Remantadine distribution in the cell-nutrient medium and in experimental animals was studied. Differences in the penetration and content of remantadine in the MDCK cells and lung of intact and influenza virus-infected white mice were demonstrated. The content of remantadine in these systems depended on the time of its administration. When remantadine was added into intact cultures or in cultures infected with influenza virus 1hr after remantadine inoculation, its content in the cells was similar, about 40% of that added to the culture medium. If remantadine was added to previously infected culture, its content in the cells was considerably lower. Similar results were obtained in experimental white mice.