In recent decades the brown hare (Lepus europaeus) population in Denmark has undergone a substantial decline, but proximate causes are unknown and little is known about actual densities. In this thesis, hare populations are investigated with respect to age composition and reproductive parameters in relation to habitat and phenotype, and point transect counts are evaluated in assessing hare densities. High spatial variation in post-natal survival of offspring is observed. Some variation in the demographic and phenotypic (size, weight) parameters is attributable to habitat composition. The juvenile proportions in game bags have dropped significantly since the 1950ies. Simple matrix population models with variable juvenile recruitment predict the similar population growth rates as actually observed in the annual bag records. The model substantiates the supposition that declines in the Danish hare population are caused by reduced juvenile recruitment. Point transect counts are suitable and corrections for detection necessary, when monitoring hare populations, but work is still needed, before the effects of e.g. road avoidance on density estimates are fully clarified.