The paper reviews information about the ash dieback including its history, geographic distribution and effects. Biology and symptoms of infection by the invasive fungus Hymenoscyphus fraxineus, the main pathogen involved in the ash dieback, are presented along with the results of recent research of interactions between the host species, the pathogen and the environment. Ways of mitigation of the effects of ash dieback are discussed subsequently. Strong genetic control of the infection-tolerance opens the possibility for selection of hyposensitive trees for the establishment of seed orchards, which will produce offspring with improved tolerance to H. fraxineus. Management strategies for the ash dieback are needed, however, in order to sustain the presence of the ash in forest stands, open landscape and urban areas. In forests, silvicultural measures could focus on the ontogenetic stages particularly threatened by the dieback, including saplings in young growths and cultures, as well as trees in the thinning-stage stands.