Using the test of indirect immunofluorescence, the authors examined sera of animals for antibodies against the strain CG 18-20 of Hantavirus (identical with strain Puumala) and against the Hantaan strain. As a control and supplement of the examination the authors used cells containing the TBE virus, strain Hypr. In a group of 260 hares (Lepus europaeus) in 3.5% antibodies were present against Hantavirus CG 18-20. Of 41 deer (Capreolus capreolus) they were present in 14.1%. Of 11 fallow-deers none had antibodies against hantaviruses. Among 145 specimens of Bos taurus antibodies were present in two incl. one against the strain Hantaan. The findings are discussed in relation to previous research of natural foci of hantavirus infections and infections with the TBE virus in Bohemia and Moravia. The paper reveals hitherto unknown localities of foci and hitherto not studied participants of the circulation of hantaviruses.