The causative agent of sooty bark disease, Cryptostroma corticale, has, for some years, caused increased damage to maples (Acerspp.) in Germany and throughout Europe. It has been stated that this pathogen can occur latently in Acer. In this study, the composition of endophytic fungi of woody stem tissues of sycamore (Acer pseudoplatanus) saplings were analysed in order to investigate whether C. corticaleis present in young, visually healthy maple trees from natural regeneration. The most abundant taxa of the 30 isolated endophytes were Diaporthecf. rudisand Petrakia irregularis. An association of five fungal species (Biscogniauxia mediterranea, Coniochaeta velutina, Gibellulopsis catenata, Neocucurbitaria quercina, Tangerinosporium thalitricola) with A. pseudoplatanuswas reported for the first time. Cryptostroma corticalewas not present in the juvenile sycamore stems. Furthermore, its pathogenicity was studied in comparison to other pathogens associated with A. pseudoplatanus, namely Diplodia mutila, Dothiorellasp., Nectria cinnabarina, Neonectria coccinea, Neonectria puniceaand Stegonsporium pyriforme. The longest necroses were induced by C. corticalefollowed by N. coccinea. In a trial with a C. corticalespore suspension sprayed directly on stem bark, the fungus could be re-isolated from woody tissue, however necroses were evoked only when the bark was wounded prior to infection. The results from the experiments presented here function as additional evidence for the ability of C. corticaleto establish endophytically within the host and, in particular, for the ability of the fungus to establish a successful infection/entrance through intact bark.