In this paper various definitions and different methods of so-called top heights are set against one another, and are compared with each other by means of examples from Swiss growth and yield research plots. Pure stands as well as even-aged and uneven-aged mixed stands are used for this purpose. It is shown that in mixed stands the manner of selection of the species involved in the top height group, reveals no appreciably different results; the variously defined top height groups are largely identical. The computation method of the mean height or the determination by the mean basal area tree of the top height group, do not influence the result appreciably. By means of examples it is shown that, especially in uneven-aged mixed stands, the various top height definitions may produce differing results.
On the basis of the results of this study and in view of the small differences, it is recommended that top heights are calculated as mean values. When different admixed tree species are considered, preference is to be given to the selection according to their actual belonging to the top height group in a stand, rather than to their proportional part of the basal- area. The selection of a generally recommended top height must be clarified in further investigations.