The genus Biscogniauxia, a member of the family Xylariaceae, has a worldwide distribution with over 50 taxa recognised. Biscogniauxia mediterranea is well known as the causative agent of charcoal canker in cork oak and is a serious problem in Portugal. Other species also cause canker under specific conditions. There is good evidence that these species occur in healthy living trees as endophytes and then become invasive under water stress conditions. The ability of B. nummularia, B. nothofagi and B. uniapiculata to cause cankers in Fagus, Nothofagus and Eucalyptus respectively is reported here.