Abstract: In Algeria, cork oak forests are an essential element of the physical, climatic and socio-economic balance of populations of the rural zones. Nonetheless, cork oaks are currently facing serious problems of dieback caused by pathogens. This study was conducted in two mountain forests: Hafir in the northwest, and Djebel Saadia in the northeast Algeria. It aims to assess i) the impact of cork oak infection by Biscogniauxia mediterranea, and ii) the state of health of the stands in each region. Sampling was carried out by recording stationary reports relating to the station, dendrometric reports (height and circumference), state of the tree (degree of dieback), and exploitation (debarked/ barked). Results showed that in the Hafir forest attacks were observed for trees of 3rd class with height of 7 to 10 m and the circumference around 70-109 cm. Trees of other categories were less attacked. At the level of the forest of Djebel Saadia, the attacked trees were young (C1) with a height less than 6 m and less than 70 cm in circumference. The infestation rate in the two forests was around 4% No difference was observed between the two study sites (Z = 0.04; P = 0.968).