Chlorophyll fluorescence induction kinetics were used to assess different features of the photosynthetic system of trees affected by forest decline and of control trees. Several parameters can be derived from the kinetics: Fo and Fo', the initial fluorescence intensity and its initial slope, the maximum intensity Fp, and the final steady- state intensity Fs. Furthermore, the ratio R(t) of the two fluorescence components at 685 nm and 730 nm shows the initial value Ro, the minimum value Rm, and the steady- state value Rs. Measurements were carried out on spruce, birch, oak, and poplar. If one considers the variation of the parameters obtained from the different tree species and the effect on the parameters due to the forest decline, the parameters Ro and Fp/Fo exhibit a maximum capability to differentiate between control trees and those affected by forest decline.