The morphogenetic bud cycle of Fagus sylvatica L. is described, and it is shown that new leaves mainly are formed during the months of June and July. However, growth of the leaf primordia mainly takes place in August and September. Already by August all primordia of the following season are fully developped in the bud, and the primordia formation for the year after next begins. From these studies it can be concluded that early summer drought reduces the number of leaves, while late summer drought more likely affects the leaf size. Syllepsis and prolepsis frequently occur together in young beech trees. Depending on the weather conditions in late summer and autumn either there will be frequent prolepsis the following autumn or frequent syllepsis the following spring. Abnormalities specific to proleptic shoots all can be explained by an incomplete development of lammas shoots in autumn. The anatomical development of the abscission zone at the base of the petiole is described including scar formation. Six phases can be distinguished. Compared with other tree species the abscission zone of Fagus sylvestica L. partly resembles that of Betula and Alnus, partly that of Quercus. The leaf abscission follows in consequence of the dissolution of the middle lamella and of parts of the primary cell wall. Time pattern and causes of leaf fall were studied in 1984 and 1985 in various beech stands. One has to distinguish strictly between a period of premature summer leaf fall and a period of early autumn leaf fall. While the former is almost exclusively caused by biotic agents (insects, fungi) and comprises only a small amount of leaves, the early autumn leaf fall can be the result of dry summers, late shooting and tree damages. However, so far no definite correlation could be detected between the degree of beech decline and the beginning of autumn leaf fall. This is difficult because already by nature the time pattern and the setting in of leaf fall vary between light and shade crown and between individual trees and stands.