The main concern of this work is to propose analytical relations describing the stabi-lity of trees depending on the dendrometry. Further, the aim is to derive allometric co-efficients of breakage and windthrow failure based on dendrometric quantities and theory of mechanics. Selected individuals of the genus maple, birch, beech, ash, oak and linden are located in urban areas of Prostějov. The allometric relationships are based on the dendrometric measurements of these individuals (a diameter, center of gravity he-ight, crown area etc.) and on mechanics (wood strength; modulus of elasticity of wood, roots and soil; inclination etc). Tree age was calculated from the relationship between the dendrometric variables. The allometric coefficients for tree assessment in the phase of maturity conditioned by tree species and the stability of the tree can not be evaluated only according to the diameter and height of the center of gravity but also according to sail area of the crown. When assesing trees not only the geometry but also material pro-perties should be considered. Of allometric relationships for breakege, windthrow and buckling I find most useful the relationship for the breakage because it uses also the sail area and material properties.