In vitro germination of conidia of Cylindrocladium quinqueseptatum Boedijn & Reitsma, a cause of leaf blight of Eucalyptus spp., began after 4.5 h of incubation and attained approx. 95 % within 8 h; germination was optimal at 25°C. Conidial germination on the intact leaves of 2‐month‐old E. grandis occurred after 3 h of incubation. Formation of appressorium over the epidermal cells was recorded first on the abaxial surface of leaves at 6 h and later on the adaxial surface. Formation of appressorium over the stomata was found only very rarely and most leaf penetrations occurred directly through epidermal cells. Copyright {\textcopyright} 1990, Wiley Blackwell. All rights reserved