ABSTRACTA method for determining the absolute age of European hares(Lepus europeus)based on periosteal growth lines in the mandible was applied on thirty‐nine hares of unknown age and twenty hares of known age, captured and marked as juveniles. Annual growth lines (adhesion lines) were found in all hares except juveniles. In 85% there were agreements between numbers of annual layers and the real ages in the hares of known age examined. Previous treatment of the bone material with hydrogen peroxide complicated age determination by this metho