The work focuses on the seasonal course of transpiration of an adult beech stand in the third forest vegetation stage (oak-breech). The theoretical part of the work is focused on the analysis of the transpiration process issue, which is influenced by the synergistic action of many factors. The work describes a system of accurate measurement of transpiration flow by heat balance method and basic methods of extrapolation of measured data on transpiration flow of individuals to the whole stand or the area of the stand. The practical part of the work is based on data on the sap flow of European beech individuals measured in situ in the experimental area of Bienska dolina (450 a.s.l.), meteorological data and seasonal development potential of soil water. We focused on measuring and investigating the transpiration of stands using the heat balance method on the research beech stand. We investigated the relationship between transcription and meteorological elements. We transferred the measured data to tables, thanks to which we found that the knowledge from the theoretical part coincides with the measurements. It has been found that the transpiration of beech stands responds to climate change and is thus largely influenced and reduced due to adverse conditions.