In this study, the variability of physiological parameters of five provenances of Europeanbeech (Fagus sylvatica), which were planted at two locations with different ecological conditions atFruška Gora and Debeli Lug, was estimated. Provenance trials were established in the framework ofCOST Action E52: "Evaluation of Beech Genetic Resources for Sustainable Forestry". 2-3 years oldseedlings originating from Croatia, Germany, Bosnia, Austria and Serbia were planted in blocks offifty plants with a spacing of 2 x 1 m. Physiological parameters such as net photosynthesis, rate oftranspiration and stomatal conductance were measured with a portable gas analysis system. Generally,provenances from Fruška Gora Mountain showed higher intensity of all physiological parameters thanprovenances located at site Debeli Lug. High correlations among rates of net photosynthesis andtranspiration, on one side, and stomatal conductance, on the other side, were found. ANOVA testindicates that variability of net photosynthesis, transpiration and stomatal conductance of investigatedprovenances, at the two locations, was influenced both by environmental conditions of sites andgenetic constitution of provenances