The 4°K_4°Ar radiometric whole-rock analyses of a series of samples mainly from lava flows intercalated between the fossiliferous sediments of several sites of the Ceske Stredohoff Mountains (Northern Bohemia) has made possible to get results generally ranging between 38 .3 ± 0.9 Ma and 23 .7 ± 1 .3 Ma. They mostly characterize Oligocene ages and, more precisely, the Stampian. They are parallelized with informations provided both by the flora and the lower vertebrate fauna (mainly the fish-fauna) of the studied fossiliferous localities. Resume. La datation isotopique 4°K_4°Ar sur roches totales d'une serie d'echantillons de laves intercalees dans les sediments fossiliferes de plusieurs sites de Ceske Stredohoff, au Nord de la Boheme a fourni des resultats compris pour la plupart entre 38,3 ± 0,9 Ma et 23,7 ± 1 ,3 Ma, ces valeurs correspondant it I 'Oligocene et plus precisement au Stampien. Les resultats obtenus sont mis en parallele avec la composi tion des flores et de la faune de vertebres inferieurs (poissons principalement) des gisements fossiliferes etudies.